ORCID Profile
0000-0001-6375-1977
Current Organisation
University of Western Australia
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Crop and Pasture Production | Plant Biology | Crop and Pasture Protection (Pests, Diseases and Weeds) | Plant Cell and Molecular Biology | Plant Protection (Pests, Diseases And Weeds) | Plant Physiology | Plant Physiology | Cell Metabolism | Gene Expression | Biological Adaptation | Genetics | Plant Biochemistry And Physiology | Plant Improvement (Selection, Breeding And Genetic Engineering) | Receptors and Membrane Biology | Enzymes | Research, Science and Technology Policy | Genome Structure | Membrane Biology | Crop and Pasture Biochemistry and Physiology | Policy and Administration | Plant Pathology | Cell Metabolism
ANZSRC Socio-Economic Objective (SEO)
Field crops | Wheat | Control of Plant Pests, Diseases and Exotic Species in Farmland, Arable Cropland and Permanent Cropland Environments | Barley | Canola | Wheat | Environmentally Sustainable Plant Production not elsewhere classified | Primary products from plants | Grain legumes | Horticultural crops | Control of pests and exotic species | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Agricultural and Veterinary Sciences | Expanding Knowledge in the Biological Sciences | Sheep—meat | Sown grasses |
Related Links
Publications
Target‐site resistance to trifluralin is more prevalent in annual ryegrass populations from Western Australia
Publisher: Wiley
Date: 12-12-2021
DOI: 10.1002/PS.6737
Abstract: Trifluralin is widely used in Australia as one of the important pre‐emergence herbicides to control annual ryegrass ( Lolium rigidum Gaud.) populations. Trifluralin resistance evolution and mechanisms have been identified in some ryegrass populations. In this study, 21 putative resistant field survey populations from Western Australian were screened with trifluralin, and 90% (19 of 21) contained in iduals surviving 480 g ha −1 trifluralin treatment. Twelve populations contained in iduals possessing the known α‐tubulin resistance mutations at Val‐202, Thr‐239 and Arg‐243 in TUA4 ( alpha ‐ tubulin 4 n ), plus multiple potential resistance mutations in TUA4 pending genetic confirmation. Three populations had only in iduals carrying newly identified (but uncharacterized) mutations in TUA3 / TUA4 . Radioactive work found that six populations evolved metabolic resistance to trifluralin, and at least four of them also possessed the known and/or putative target‐site mutations. These results confirm that a high incidence of resistance to the dinitroaniline herbicide (trifluralin) is present, and target‐site tubulin mutations make a major contribution to resistance in these annual ryegrass populations. Co‐evolution of both target‐site and non‐target‐site resistance to per‐emergence herbicides warrants erse management tactics.
PIM (Poppy Integrated Management): a bio‐economic decision support model for the management of Papaver rhoeas in rain‐fed cropping systems
Publisher: Wiley
Date: 15-03-2010
Effects of Photoinhibition Induced by Water Stress on Growth and Yield of Grain Sorghum
Publisher: CSIRO Publishing
Date: 1988
DOI: 10.1071/PP9880179
Abstract: The significance of photoinhibition induced by water stress for growth and grain yield of sorghum was investigated by shading water-stressed plants for a 7-day period during panicle development. Thereafter, shading was removed, stressed plants were rewatered, and all plants were kept well-watered until physiological maturity. Shading water-stressed plants for a 7-day period increased grain number and grain yield of primary heads by 10- and 13-fold, respectively. Even though plants were severely stressed, photoinhibition was only 20%. Moreover, reduction of photoinhibition by shading did not improve carbon supply to the developing panicle. Therefore, the response of grain yield to shading was attributed to a 15% higher average leaf water potential in shaded plants, which arose despite attempts to keep water status similar in shaded and unshaded plants. The effect of water stress on the primary head was so severe that many plants produced secondary heads. The grain yield from these secondary heads compensated for the low yield of primary heads so that the total dry matter production and total grain yield of water-stressed plants were similar to those of unstressed plants. In view of the ability of this relatively determinate species to compensate for potential yield losses, as well as the mechanisms to avoid water stress, high temperatures and excessive absorption of light, it seems unlikely that photoinhibition induced by water stress will be of agronomic significance in grain sorghum.
Identification of Genetic Elements Associated with EPSPS Gene Amplification
Publisher: Public Library of Science (PLoS)
Date: 10-06-2013
Resistance to the Herbicide Paraquat and Increased Tolerance to Photoinhibition Are Not Correlated in Several Weed Species
Publisher: Oxford University Press (OUP)
Date: 05-1991
DOI: 10.1104/PP.96.1.314
Resistance evaluation for herbicide resistance–endowing acetolactate synthase (ALS) gene mutations using Raphanus raphanistrum populations homozygous for specific ALS mutations
Publisher: Wiley
Date: 02-2012
PAM: Decision Support for Long-Term Palmer Amaranth (Amaranthus palmeri) Control
Publisher: Cambridge University Press (CUP)
Date: 19-10-2017
DOI: 10.1017/WET.2017.69
Abstract: Palmer amaranth is the most troublesome weed problem in mid-southern US crop production. Herbicides continue to be the most commonly employed method for managing Palmer amaranth, despite the weed’s widespread resistance to them. Therefore, farmers need research and extension efforts that promote the adoption of integrated weed management (IWM) techniques. Producers, crop consultants, educators, and researchers would be more likely to deploy ersified chemical and nonchemical weed management options if they are more informed about long-term biological and economic implications via user-friendly decision-support software. Described within is a recently developed software that demonstrates the effects of Palmer amaranth management practices on soil seedbank, risk of resistance evolution, and economics over a 10-year planning horizon. Aiding this objective is a point-and-click interface that provides feedback on resistance risk, yield potential, profitability, soil seedbank dynamics, and error checking of management options.
Dinitroaniline herbicide resistance in a multiple‐resistant Lolium rigidum population
Publisher: Wiley
Date: 02-2018
DOI: 10.1002/PS.4790
Abstract: The pre-emergence dinitroaniline herbicides (such as trifluralin and pendimethalin) are vital to Australian no-till farming systems. A Lolium rigidum population collected from the Western Australian grain belt with a 12-year trifluralin use history was characterised for resistance to dinitroaniline, acetyl CoA carboxylase (ACCase)- and acetolactate synthase (ALS)-inhibiting herbicides. Target-site resistance mechanisms were investigated. This L. rigidum population exhibited 32-fold resistance to trifluralin, as compared with the susceptible population. It also displayed 12- to 30-fold cross-resistance to other dinitroaniline herbicides (pendimethalin, ethalfluralin and oryzalin). In addition, this population showed multiple resistance to commonly used post-emergence ACCase- and ALS-inhibiting herbicides. Two target-site α-tubulin gene mutations (Val-202-Phe and Thr-239-Ile) previously documented in other dinitroaniline-resistant weed species were identified, and some known target-site mutations in ACCase (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg) and ALS (Pro-197-Gln/Ser) were found in the same population. An agar-based Petri dish screening method was established for the rapid diagnosis of resistance to dinitroaniline herbicides. Evolution of target-site resistance to both pre- and post-emergence herbicides was confirmed in a single L. rigidum population. The α-tubulin mutations Val-202-Phe and Thr-239-Ile, documented here for the first time in L. rigidum, are likely to be responsible for dinitroaniline resistance in this population. Early detection of dinitroaniline herbicide resistance and integrated weed management strategies are needed to maintain the effectiveness of dinitroaniline herbicides. © 2017 Society of Chemical Industry.
Harrington Seed Destructor: A New Nonchemical Weed Control Tool for Global Grain Crops
Publisher: Wiley
Date: 05-2012
Glyphosate resistance in Sorghum halepense and Lolium rigidum is reduced at suboptimal growing temperatures
Publisher: Wiley
Date: 17-12-2012
DOI: 10.1002/PS.3464
Abstract: Glyphosate resistance in populations of the C(4) perennial Sorghum halepense (Johnsongrass) and C(3) annual Lolium rigidum (rigid ryegrass) has evolved and been documented in many cropping areas around the globe. In S. halepense and in the majority of reported cases in L. rigidum the glyphosate resistance trait has been associated with a mechanism that reduces glyphosate translocation within plants. Here, the significant decrease in the glyphosate resistance level when resistant plants of S. halepense and L. rigidum are grown at suboptimal cool temperature conditions is reported. Lowering temperature from 30 to 19 °C in S. halepense and from 19 to 8 °C in L. rigidum significantly reduced both plant survival and above-ground biomass produced by glyphosate-resistant plants. Thus, glyphosate resistance parameters significantly decreased when glyphosate-treated resistant plants of both species were grown under non-optimal temperature conditions. The results suggest that the resistance mechanism against glyphosate damage is less efficient at sub-optimal [corrected] growing temperatures. It is possible to increase the control of glyphosate-resistant S. halepense and L. rigidum populations by treatment with glyphosate during growing conditions at suboptimal low temperatures. Conversely, glyphosate failure will continue to occur on glyphosate-resistant populations treated during periods of higher temperatures
Targeting key perceptions when planning and evaluating extension
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/EA04102
Abstract: Early identification of farmer perceptions influencing particular farm management decisions provides the opportunity to more effectively focus investment in research and extension. A survey-based study examining the adoption of integrated weed management by Western Australian grain growers was used to demonstrate how identification of key farmer perceptions can help to guide research and extension priorities. It was found that the adoption of integrated weed management practices was influenced by grower perceptions of herbicide resistance-related factors and of the efficacy and economic value of integrated weed management practices in the farming system. However, there were generally no significant differences between the perceptions of practice efficacy held by users and non-users of the integrated weed management practices. As initial perceptions of efficacy were generally consistent with local field experience, it was expected that extension would not have a major influence on this variable. Consistent with this, participation by growers in a workshop based on the bio-economic farming systems model, resistance integrated management (RIM), did not result in changes in perceptions of practice efficacy. However, changes in the perceived short-term economic value of some weed management practices did occur where the broader value of practices to the farming system, not necessarily relating to weed control, could be demonstrated. This also led to more growers deciding to adopt those practices. For ex le, intended wheat seeding rates were shown to increase by 5 kg/ha as a result of participation in the extension activity. Determining the perceptions influencing adoption, and then identifying the major learning opportunities can be valuable in focusing research and extension. Measures of perceptions also allow learning to be evaluated. In the case study of adoption of the integrated weed management practices in WA, it seems that emphasis on developing and extending the farming-systems impacts beyond just weed and resistance management is likely to be more effective than focusing on the efficacy of the practices for controlling major weeds.
Affective facial expression processing via simulation: A probabilistic model
Publisher: Elsevier BV
Date: 10-2014
Understanding the potential for resistance evolution to the new herbicide pyroxasulfone: field selection at high doses versus recurrent selection at low doses
Publisher: Wiley
Date: 10-2012
Multiple resistance across glufosinate, glyphosate, paraquat and ACC ase‐inhibiting herbicides in an E leusine indica population
Publisher: Wiley
Date: 22-10-2014
DOI: 10.1111/WRE.12118
Evolution of Glyphosate-Resistant Johnsongrass (Sorghum halepense) in Glyphosate-Resistant Soybean
Publisher: Cambridge University Press (CUP)
Date: 12-2007
DOI: 10.1614/WS-07-053.1
Abstract: In Argentinean crop fields, weed control is mainly achieved by intense use of glyphosate as a nonselective and/or selective herbicide. Glyphosate use is very high as more than 95% of the 16 million ha soybean crop consists of glyphosate-resistant cultivars, always treated with this herbicide. From initial success, inconsistent glyphosate control of Johnsongrass, an invading C4 perennial grass of soybean crops, has become evident to producers from northern Argentina over the last 3 yr. Prior to this, glyphosate provided good control. This study evaluated the nature of these recurrent glyphosate failures in Johnsongrass. Experiments conducted with Johnsongrass plants obtained from seed and rhizome phytomers collected from fields with intense glyphosate use history showed that these populations showed differential survival and biomass productivity when glyphosate treated than Johnsongrass plants obtained from similar propagules collected from field sites with no history of glyphosate use. This empirical evidence establishes that the Johnsongrass survival in glyphosate-treated transgenic soybean fields from northern Argentina is due to evolved glyphosate resistance.
Enhanced Trifluralin Metabolism Can Confer Resistance in Lolium rigidum
Publisher: American Chemical Society (ACS)
Date: 02-07-2018
Abstract: Resistance to the pre-emergence herbicide trifluralin is increasing in Australian annual ryegrass ( Lolium rigidum) populations. Three L. rigidum populations (R1, R2, and R3) collected from Australian grain fields were identified with trifluralin resistance. Both target-site and nontarget-site resistance mechanisms were investigated. No target-site α-tubulin mutations were detected in populations R1 and R3, while an Arg-243-Lys mutation was found in R2. Compared with the three trifluralin-susceptible populations, enhanced [
A potential role for endogenous microflora in dormancy release, cytokinin metabolism and the response to fluridone in Lolium rigidum seeds
Publisher: Oxford University Press (OUP)
Date: 02-12-2014
DOI: 10.1093/AOB/MCU231
I remember what you did: A behavioural guide-robot
Publisher: Springer International Publishing
Date: 31-05-2019
Attempts to transfer paraquat resistance from barley grass (Hordeum glaucum Steud.) to barley and wheat
Publisher: Wiley
Date: 12-1991
Herbicide Resistance Endowed by Enhanced Rates of Herbicide Metabolism in Wild Oat (Avenaspp.)
Publisher: Cambridge University Press (CUP)
Date: 03-2013
Abstract: The biochemical basis of resistance to the acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide diclofop-methyl was investigated in a resistant wild oat population (R1), which does not exhibit a resistant ACCase. Rates of foliar uptake and translocation of [ 14 C]-diclofop were the same in the R1 vs. susceptible (S) populations. However, the level of phytotoxic diclofop acid was always found to be lower in the R1 vs. S plants, with a concomitant higher level (up to 1.7-fold) of nontoxic polar diclofop metabolites in R1 relative to the S plants. These results indicate that a non–target-site-based mechanism of enhanced rate of diclofop acid metabolism confers resistance in population R1. Moreover, the high-performance liquid chromotography elution profile of the major diclofop metabolites in R1 is similar to that of wheat, suggesting resistance in in iduals of population R1 involves a wheat-like detoxification system mediated by cytochrome P450 monooxygenases. In addition, lower level of tissue diclofop acid was also observed using nonradioactive ultra-performance liquid chromatography–mass spectrometry analysis in resistant in iduals of three other resistant wild oat populations (R2, R3, and R4) known to posses ACCase gene resistance mutations. These results establish that either one or at least two independent resistance mechanisms (target-site ACCase resistance mutations and non–target-site enhanced rates of herbicide metabolism) can be present in in idual wild oat plants.
Simulation modelling identifies polygenic basis of herbicide resistance in a weed population and predicts rapid evolution of herbicide resistance at low herbicide rates
Publisher: Elsevier BV
Date: 10-2012
Dark-mediated dormancy release in stratified Lolium rigidum seeds is associated with higher activities of cell wall-modifying enzymes and an apparent increase in gibberellin sensitivity
Publisher: Elsevier BV
Date: 04-2011
DOI: 10.1016/J.JPLPH.2010.09.001
Abstract: Dormancy release in freshly matured, imbibed annual ryegrass (Lolium rigidum) seeds is inhibited by light and involves a decrease in seed sensitivity to abscisic acid. Other processes involved in dormancy release in the dark were investigated by measuring seed storage compound mobilisation and the activity of cell wall-degrading enzymes. Activities of endo-β-mannanase and total peroxidase were higher in dark-stratified compared to light-stratified seeds, indicating that weakening of the structures constraining the embryo was accelerated in the dark. A dramatic degradation of storage proteins in light-stratified seeds, accompanied by induction of a high molecular mass protease, suggests that maintenance of storage(-like) proteins is also important in dark-mediated dormancy release. α-Amylase activity was induced in dark-stratified seeds at least 48 h prior to radicle emergence upon transfer to conditions permitting germination, or in light-stratified seeds supplied with exogenous gibberellin A(4). This suggests that (a) α-amylase is involved in stimulation of germination of non-dormant L. rigidum seeds, and (b) dark-stratified seeds have an increased sensitivity to gibberellins which permits the rapid induction of α-amylase activity upon exposure to germination conditions. Overall, it appears that a number of processes, although possibly minor in themselves, occur in concert during dark-stratification to contribute to dormancy release.
Harvest weed seed control: impact on weed management in Australian grain production systems and potential role in global cropping systems
Publisher: CSIRO Publishing
Date: 23-02-2022
DOI: 10.1071/CP21647
Abstract: The introduction of harvest weed seed control (HWSC) techniques and associated machinery has enabled the routine use of an alternative weed control technology at a novel weed control timing in global grain cropping fields. Driven by the significant threat of widespread populations of annual ryegrass (Lolium rigidum) with multiple-herbicide resistance, in the 1990s Australian growers and researchers developed techniques to target, at grain harvest, the seed production of annual ryegrass and other important weed species. The HWSC approach to weed management is now routinely used by a majority of Australian grain producers as an integral component of effective weed control programs. Here we detail the development and introduction of current HWSC systems and describe their efficacy in Australian grain production systems. The use of HWSC has likely contributed to lower annual ryegrass population densities and thus mitigated the impacts of herbicide resistance as well as slowing further evolution of resistance. In addition, low weed densities enable the introduction of site-specific weed control technologies and the opportunity to target specific in-crop weeds with non-selective alternative weed control techniques. With an awareness of the evolutionary potential of weed species to adapt to all forms of weed control, there is an understanding that HWSC treatments need to be judiciously used in grain cropping systems to ensure their ongoing efficacy. The successful use of Australian developed HWSC systems has attracted global interest and there is now a considerable international research effort aimed at introducing this alternative weed control approach and timing into the world’s major cropping systems.
No fitness cost of glyphosate resistance endowed by massive EPSPS gene amplification in Amaranthus palmeri
Publisher: Springer Science and Business Media LLC
Date: 03-01-2014
DOI: 10.1007/S00425-013-2022-X
Abstract: Amplification of the EPSPS gene has been previously identified as the glyphosate resistance mechanism in many populations of Amaranthus palmeri, a major weed pest in US agriculture. Here, we evaluate the effects of EPSPS gene lification on both the level of glyphosate resistance and fitness cost of resistance. A. palmeri in iduals resistant to glyphosate by expressing a wide range of EPSPS gene copy numbers were evaluated under competitive conditions in the presence or absence of glyphosate. Survival rates to glyphosate and fitness traits of plants under intra-specific competition were assessed. Plants with higher lification of the EPSPS gene (53-fold) showed high levels of glyphosate resistance, whereas less lification of the EPSPS gene (21-fold) endowed a lower level of glyphosate resistance. Without glyphosate but under competitive conditions, plants exhibiting up to 76-fold EPSPS gene lification exhibited similar height, and biomass allocation to vegetative and reproductive organs, compared to glyphosate susceptible A. palmeri plants with no lification of the EPSPS gene. Both the additive effects of EPSPS gene lification on the level of glyphosate resistance and the lack of associated fitness costs are key factors contributing to EPSPS gene lification as a widespread and important glyphosate resistance mechanism likely to become much more evident in weed plant species.
Evolution of a Double Amino Acid Substitution in the 5-Enolpyruvylshikimate-3-Phosphate Synthase in Eleusine indica Conferring High-Level Glyphosate Resistance
Publisher: Oxford University Press (OUP)
Date: 25-02-2015
DOI: 10.1104/PP.15.00146
Abstract: Glyphosate is the most important and widely used herbicide in world agriculture. Intensive glyphosate selection has resulted in the widespread evolution of glyphosate-resistant weed populations, threatening the sustainability of this valuable once-in-a-century agrochemical. Field-evolved glyphosate resistance due to known resistance mechanisms is generally low to modest. Here, working with a highly glyphosate-resistant Eleusine indica population, we identified a double amino acid substitution (T102I + P106S [TIPS]) in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene in glyphosate-resistant in iduals. This TIPS mutation recreates the biotechnology-engineered commercial first generation glyphosate-tolerant EPSPS in corn (Zea mays) and now in other crops. In E. indica, the naturally evolved TIPS mutants are highly (more than 180-fold) resistant to glyphosate compared with the wild type and more resistant (more than 32-fold) than the previously known P106S mutants. The E. indica TIPS EPSPS showed very high-level (2,647-fold) in vitro resistance to glyphosate relative to the wild type and is more resistant (600-fold) than the P106S variant. The evolution of the TIPS mutation in crop fields under glyphosate selection is likely a sequential event, with the P106S mutation being selected first and fixed, followed by the T102I mutation to create the highly resistant TIPS EPSPS. The sequential evolution of the TIPS mutation endowing high-level glyphosate resistance is an important mechanism by which plants adapt to intense herbicide selection and a dramatic ex le of evolution in action.
Loss of trifluralin metabolic resistance in Lolium rigidum plants exposed to prosulfocarb recurrent selection
Publisher: Wiley
Date: 07-08-2020
DOI: 10.1002/PS.5993
A novel psbA mutation (Phe274–Val) confers resistance to PSII herbicides in wild radish (Raphanus raphanistrum )
Publisher: Wiley
Date: 30-07-2018
DOI: 10.1002/PS.5079
Abstract: Wild radish (Raphanus raphanistrum) is a globally important weed of crops. Two atrazine-resistant wild radish populations (R1 and R2), collected from the Western Australia grain belt, were investigated for resistance to photosystem II (PSII) herbicides. Sequencing of the full-length psbA gene revealed the well-known Ser264-Gly substitution in population R1, whereas population R2 displayed a novel Phe274-Val substitution. Herbicide dose-response studies confirmed that the population with the Ser264-Gly mutation exhibited high-level resistance to atrazine, but super-sensitivity to bromoxynil. Plants possessing the novel Phe274-Val mutation exhibited a modest level of resistance to atrazine, metribuzin and diuron, and were bromoxynil susceptible. Structural modelling of the mutant D1 proteins predicts that the Ser264-Gly mutation endows atrazine resistance by abolishing H-bonds, but confers bromoxynil super-sensitivity by enhancing hydrogen bonding. The Phe274-Val substitution provides resistance to atrazine and diuron by indirectly affecting H-bond formation between the Ser264 residue and the herbicides. The results demonstrate that the Phe274-Val mutation is likely responsible for resistance to PSII-inhibiting triazine and urea herbicides. To our knowledge, this is the first evidence of the psbA Phe274-Val mutation in wild radish conferring resistance to PSII herbicides. © 2018 Society of Chemical Industry.
High survival frequencies at low herbicide use rates in populations of Lolium rigidum result in rapid evolution of herbicide resistance
Publisher: Springer Science and Business Media LLC
Date: 21-09-2005
Abstract: The frequency of phenotypic resistance to herbicides in previously untreated weed populations and the herbicide dose applied to these populations are key determinants of the dynamics of selection for resistance. In total, 31 Lolium rigidum populations were collected from sites with no previous history of exposure to herbicides and where there was little probability of gene flow from adjacent resistant populations. The mean survival frequency across all 31 populations following two applications of commercial rates (375 g ha(-1)) of the acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicide, diclofop-methyl was 0.43%. Survivors from five of these populations were grown to maturity and seed was collected. Dose-response experiments compared population level resistance to diclofop-methyl in these selected lines with their original parent populations. A single cycle of herbicide selection significantly increased resistance in all populations (LD(50) R:S ratios ranged from 2.8 to 23.2), confirming the inheritance and genetic basis of phenotypic resistance. In vitro assays of ACCase inhibition by diclofop acid indicated that resistance was due to a non-target-site mechanism. Following selection with diclofop-methyl, the five L. rigidum populations exhibited erse patterns of cross-resistance to ACCase and ALS-inhibiting herbicides, suggesting that different genes or gene combinations were responsible for resistance. The relevance of these results to the management of herbicide resistance are discussed.
Multiple Metabolic Enzymes Can Be Involved in Cross-Resistance to 4-Hydroxyphenylpyruvate-Dioxygenase-Inhibiting Herbicides in Wild Radish
Publisher: American Chemical Society (ACS)
Date: 11-05-2023
Grain grower perceptions and use of integrated weed management
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/EA03115
Abstract: Greater adoption of integrated weed management, to reduce herbicide reliance, is an objective of many research and extension programmes. In Australian grain-growing regions, integrated weed management is particularly important for the management of herbicide resistance in weeds. In this study, survey data from personal interviews with 132 Western Australian grain growers are used to characterise the use and perceptions of integrated weed management practices. The main objective was to identify opportunities for improved weed management decision making, through targeted research and extension. The extent to which integrated weed management practices are used on in idual farms was measured. Perceptions of the efficacy and reliability of various weed management practices were elicited for control of annual ryegrass (Lolium rigidum Gaud.), along with perceptions of the economic value of integrated weed management practices relative to selective herbicides. All growers were shown to be using several integrated weed management practices, although the use of some practices was strongly associated with the presence of a herbicide-resistant weed population. In general, both users and non-users were found to have high levels of awareness of integrated weed management practices and their weed control efficacy. Herbicide-based practices were perceived to be the most cost-effective. Opportunities for greater adoption of integrated weed management practices, to conserve the existing herbicide resource, exist where practices can be shown to offer greater shorter-term economic value, not necessarily just in terms of weed control, but to the broader farming system.
Mutations of the ALS gene endowing resistance to ALS‐inhibiting herbicides in Lolium rigidum populations
Publisher: Wiley
Date: 17-07-2008
DOI: 10.1002/PS.1624
Abstract: In the important grass weed Lolium rigidum (Gaud.), resistance to ALS-inhibiting herbicides has evolved widely in Australia. The authors have previously characterised the biochemical basis of ALS herbicide resistance in a number of L. rigidum biotypes and established that resistance can be due to a resistant ALS and/or enhanced herbicide metabolism. The purpose of this study was to identify specific resistance-endowing ALS gene mutation(s) in four resistant populations and to develop PCR-based molecular markers. Six resistance-conferring ALS mutations were identified: Pro-197-Ala, Pro-197-Arg, Pro-197-Gln, Pro-197-Leu, Pro-197-Ser and Trp-574-Leu. All six mutations were found in one population (WLR1). Each Pro-197 mutation conferred resistance to the sulfonylurea (SU) herbicide sulfometuron, whereas the Trp-574-Leu mutation conferred resistance to both sulfometuron and the imidazolinone (IMS) herbicide imazapyr. A derived cleaved lified polymorphic sequences (dCAPS) marker was developed for detecting resistance mutations at Pro-197. Furthermore, cleaved lified polymorphic sequences (CAPS) markers were developed for detecting each of the six mutant resistant alleles. Using these markers, the authors revealed erse ALS-resistant alleles and genotypes in these populations and related them directly to phenotypic resistance to ALS-inhibiting herbicides. This study established the existence of a ersity of ALS gene mutations endowing resistance in L. rigidum populations: 1-6 different mutations were found within single populations. At field herbicide rates, resistance profiles were determined more by the specific mutation than by whether plants were homo- or heterozygous for the mutation.
Enhanced rates of herbicide metabolism in low herbicide‐dose selected resistant Lolium rigidum
Publisher: Wiley
Date: 11-2012
DOI: 10.1111/PCE.12017
Abstract: Lolium rigidum is an obligately cross-pollinated, genetically erse species and an economically important herbicide resistance-prone weed. Our previous work has demonstrated that recurrent selection of initially susceptible L. rigidum populations with low herbicide rates results in rapid herbicide resistance evolution. Here we report on the mechanisms endowing low-dose-selected diclofop-methyl resistance in L. rigidum. Results showed that resistance was not due to target-site ACCase mutations or overproduction, or differential herbicide leaf uptake and translocation. The in vivo de-esterification of diclofop-methyl into phytotoxic diclofop acid was rapid and similar in resistant versus susceptible populations. However, further metabolism of diclofop acid into non-toxic metabolites was always faster in resistant plants than susceptible plants, resulting in up to 2.6-fold lower level of diclofop acid in resistant plants. This corresponded well with up to twofold higher level of diclofop acid metabolites in resistant plants. The major polar metabolites of diclofop acid chromatographically resembled those of wheat, a naturally tolerant species. Clearly, recurrent selection at reduced herbicide rates selected for non-target-site-based enhanced rates of herbicide metabolism, likely involving cytochrome P450 monooxygenases.
Mechanistic basis for synergism of 2,4-D amine and metribuzin in <i>Avena sterilis</i>
Publisher: Pesticide Science Society of Japan
Date: 20-11-2020
Directing human attention with pointing
Publisher: IEEE
Date: 08-2014
Global Herbicide Resistance Challenge
Publisher: Wiley
Date: 17-07-2014
DOI: 10.1002/PS.3808
Metabolism-Based Herbicide Resistance and Cross-Resistance in Crop Weeds: A Threat to Herbicide Sustainability and Global Crop Production
Publisher: Oxford University Press (OUP)
Date: 08-08-2014
Abstract: Weedy plant species that have evolved resistance to herbicides due to enhanced metabolic capacity to detoxify herbicides (metabolic resistance) are a major issue. Metabolic herbicide resistance in weedy plant species first became evident in the 1980s in Australia (in Lolium rigidum) and the United Kingdom (in Alopecurus myosuroides) and is now increasingly recognized in several crop-weed species as a looming threat to herbicide sustainability and thus world crop production. Metabolic resistance often confers resistance to herbicides of different chemical groups and sites of action and can extend to new herbicide(s). Cytochrome P450 monooxygenase, glycosyl transferase, and glutathione S-transferase are often implicated in herbicide metabolic resistance. However, precise biochemical and molecular genetic elucidation of metabolic resistance had been stalled until recently. Complex cytochrome P450 superfamilies, high genetic ersity in metabolic resistant weedy plant species (especially cross-pollinated species), and the complexity of genetic control of metabolic resistance have all been barriers to advances in understanding metabolic herbicide resistance. However, next-generation sequencing technologies and transcriptome-wide gene expression profiling are now revealing the genes endowing metabolic herbicide resistance in plants. This Update presents an historical review to current understanding of metabolic herbicide resistance evolution in weedy plant species.
Cross-Resistance to Herbicides in Annual Ryegrass (Lolium rigidum)
Publisher: Oxford University Press (OUP)
Date: 11-1990
DOI: 10.1104/PP.94.3.1180
Investigations into the mechanism of glyphosate resistance in Lolium rigidum
Publisher: Elsevier BV
Date: 10-2002
Lessons learnt: crop-seed cleaning reduces weed-seed contamination in Western Australian grain samples
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CP20093
Abstract: Weeds are a major contributing factor to crop yield loss. Weed control is regularly practiced during the growing season, with many growers making a conscious effort to minimise weed-seed return to the soil seedbank during the cropping program. However, growers may be unintentionally introducing weed seeds through sowing of contaminated crop seed. Using s les of crop seed obtained from 29 growers across two Western Australian grain-growing regions, 81 s les were hand-cleaned to determine weed-seed contamination levels. Of those s les, 41% were weed-free, and in the remaining 59%, the main contaminant was Lolium rigidum (annual ryegrass), occurring in 49% of contaminated s les. Crop type and cleaning method had significant effects on the level of weed-seed contamination, with barley having higher levels of contamination than other crops, and professional contractors providing lower contamination than other methods of cleaning. However, any seed-cleaning method provided significantly cleaner grain s les than no seed cleaning. This study established that crop-seed contamination was evident on Western Australian farms and that growers may be unintentionally sowing weed seeds with their crops. Seed cleaning combined with judicious paddock selection and weed-seed removal during the growing season can lead to weed-free crop seed.
An Isoleucine Residue within the Carboxyl-Transferase Domain of Multidomain Acetyl-Coenzyme A Carboxylase Is a Major Determinant of Sensitivity to Aryloxyphenoxypropionate But Not to Cyclohexanedione
Publisher: Oxford University Press (OUP)
Date: 07-2003
Abstract: A 3,300-bp DNA fragment encoding the carboxyl-transferase domain of the multidomain, chloroplastic acetyl-coenzyme A carboxylase (ACCase) was sequenced in aryloxyphenoxypropionate (APP)-resistant and -sensitive Alopecurus myosuroides (Huds.). No resistant plant contained an Ile-1,781-Leu substitution, previously shown to confer resistance to APPs and cyclohexanediones (CHDs). Instead, an Ile-2,041-Asn substitution was found in resistant plants. Phylogenetic analysis of the sequences revealed that Asn-2,041 ACCase alleles derived from several distinct origins. Allele-specific polymerase chain reaction associated the presence of Asn-2,041 with seedling resistance to APPs but not to CHDs. ACCase enzyme assays confirmed that Asn-2,041 ACCase activity was moderately resistant to CHDs but highly resistant to APPs. Thus, the Ile-2,041-Asn substitution, which is located outside a domain previously shown to control sensitivity to APPs and CHDs in wheat (Triticum aestivum), is a direct cause of resistance to APPs only. In known multidomain ACCases, the position corresponding to the Ile/Asn-2,041 residue in A. myosuroides is occupied by an Ile or a Val residue. In Lolium rigidum (Gaud.), we found Ile-Asn and Ile-Val substitutions. The Ile-Val change did not confer resistance to the APP clodinafop, whereas the Ile-Asn change did. The position and the particular substitution at this position are of importance for sensitivity to APPs.
Resistance to ACCase-inhibiting herbicides in sprangletop (Leptochloa chinensis)
Publisher: Cambridge University Press (CUP)
Date: 05-2005
DOI: 10.1614/WS-04-164R
Paraquat resistance in a population of Lolium rigidum
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/FP03234
Abstract: The first case of field-evolved paraquat resistance in a population of Lolium rigidum Gaud. (from the Western Cape, South Africa) was confirmed and the mechanism of resistance investigated. The LD50 for the resistant population (R) was 404 g ha–1, some 14 times greater than for the herbicide-susceptible (S) population (30 g ha–1). In addition, the R population was found to be more resistant to paraquat when kept at low temperature (15°C) than when kept at 30°C after paraquat treatment. The R population is normally affected by herbicides with other modes of action. No differences were found in the interaction of paraquat with Photosystem I in thylakoids isolated from the R and the S populations. Constitutive levels of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) did not differ significantly between the two populations and these enzymes responded similarly to paraquat treatment. When [14C] paraquat was applied as droplets to intact plant leaves, similar leaf uptake of [14C] paraquat occurred in the R and S populations. However, quantification data and phosphor imaging revealed restricted translocation of [14C] paraquat to untreated leaves in the R compared to S population. The results of this study with this resistant L. rigidum population from South Africa resemble those found in R biotypes of Hordeum spp. from Australia. The resistance is suggested to be primarily due to sequestration of paraquat, limiting its translocation within the plants. The exact site and mechanism of paraquat sequestration remains to be determined.
RIM: Anatomy of a Weed Management Decision Support System for Adaptation and Wider Application
Publisher: Cambridge University Press (CUP)
Date: 09-2015
Abstract: RIM, or “Ryegrass Integrated Management,” is a model-based software allowing users to conveniently test and compare the long-term performance and profitability of numerous ryegrass control options used in Australian cropping systems. As a user-friendly decision support system that can be used by farmers, advisers, and industry professionals, RIM can aid the delivery of key recommendations among the agricultural community for broadacre cropping systems threatened by herbicide resistance. This paper provides advanced users and future developers with the keys to modify the latest version of RIM in order to facilitate future updates, modifications, and adaptations to other situations. The various components of RIM are mapped and explained, and the key principles underlying the construction of the model are explained. The implementation of RIM into a Microsoft Excel® software format is also documented, with details on how user inputs are coded and parameterized. An overview of the biological, agronomic, and economic components of the model is provided, with emphasis on the ryegrass biological characteristics most critical for its effective management. The extreme variability of these parameters and the subsequent limits of RIM are discussed. The necessary compromises were achieved by emphasizing the primary end-use of the program as a decision support system for farmers and advisors.
Appearance of a biotype of the weed, Hordeum glaucum Steud., resistant to the herbicide paraquat
Publisher: Wiley
Date: 06-1986
Gene flow increases the initial frequency of herbicide resistance alleles in unselected Lolium rigidum populations
Publisher: Elsevier BV
Date: 08-2011
Amitrole Inhibits Diclofop Metabolism and Synergises Diclofop-methyl in a Diclofop-methyl-resistant Biotype ofLolium rigidum
Publisher: Elsevier BV
Date: 12-1998
Seeds of Brassicaceae weeds have an inherent or inducible response to the germination stimulant karrikinolide
Publisher: Oxford University Press (OUP)
Date: 05-08-2011
DOI: 10.1093/AOB/MCR198
Cross-Resistance to Herbicides in Annual Ryegrass (Lolium rigidum)
Publisher: Oxford University Press (OUP)
Date: 11-1991
DOI: 10.1104/PP.97.3.1035
Necessary conditions on the lifting scheme for existence of wavelets in L/sub 2/(R)
Publisher: IEEE
Date: 2000
Persistence and management of enhanced carbetamide biodegradation in soil
Publisher: Wiley
Date: 18-08-2001
Recurrent selection with reduced herbicide rates results in the rapid evolution of herbicide resistance in Lolium rigidum
Publisher: Springer Science and Business Media LLC
Date: 09-03-2005
DOI: 10.1007/S00122-005-1947-2
Abstract: There has been much debate regarding the potential for reduced rates of herbicide application to accelerate evolution of herbicide resistance. We report a series of experiments that demonstrate the potential for reduced rates of the acetyl-co enzyme A carboxylase (ACCase)-inhibiting herbicide diclofop-methyl to rapidly select for resistance in a susceptible biotype of Lolium rigidum. Thirty-six percent of in iduals from the original VLR1 population survived application of 37.5 g diclofop-methyl ha(-1) (10% of the recommended field application rate). These in iduals were grown to maturity and bulk-crossed to produce the VLR1 low dose-selected line VLR1 (0.1). Subsequent comparisons of the dose-response characteristics of the original and low dose-selected VLR1 lines demonstrated increased tolerance of diclofop-methyl in the selected line. Two further rounds of selection produced VLR1 lines that were resistant to field-applied rates of diclofop-methyl. The LD50 (diclofop-methyl dose required to cause 50% mortality) of the most resistant line was 56-fold greater than that of the original unselected VLR1 population, indicating very large increases in mean population survival after three cycles of selection. In vitro ACCase inhibition by diclofop acid confirmed that resistance was not due to an insensitive herbicide target-site. Cross-resistance studies showed increases in resistance to four herbicides: fluazifop-P-butyl, haloxyfop-R-methyl, clethodim and imazethapyr. The potential genetic basis of the observed response and implications of reduced herbicide application rates for management of herbicide resistance are discussed.
Inheritance of 2,4-D resistance traits in multiple herbicide- resistant Raphanus raphanistrum populations
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.PLANTSCI.2017.01.003
Abstract: A relatively low number of weed species have evolved resistance to auxinic herbicides despite their use for almost 70 years. This inheritance study with two Raphanus raphanistrum populations multiple-resistant 2,4-D and the ALS-inhibiting herbicide chlorsulfuron determined the number of genes and genetic dominance of 2,4-D resistance and investigated the association between traits conferring resistance to the two herbicide modes of action. Levels of 2,4-D phenotypic resistance and resistance segregation patterns were assessed in parental populations, F
Towards large-scale prediction of Lolium rigidum emergence. I. Can climate be used to predict dormancy parameters?
Publisher: Wiley
Date: 05-11-2011
Multiple herbicide-resistant wild radish (Raphanus raphanistrum) populations dominate Western Australian cropping fields
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CP15063
Abstract: Raphanus raphanistrum is a problematic weed, which has become increasingly difficult to control in Australian cropping regions. In 2010, a random survey was conducted across 14 million ha of the Western Australian grain belt to establish the frequency of herbicide resistance in R. raphanistrum and to monitor the change in resistance levels by comparing results with a previous survey in 2003. Screening R. raphanistrum populations with herbicides commonly used to control this weed revealed that most populations (84%) contained in idual plants resistant to the acetolactate synthase-inhibiting herbicide chlorsulfuron, whereas 49% of populations also had plants resistant to the imidazolinone herbicides. Resistance to other mode of action herbicides (2,4-D (76%) and diflufenican (49%)) was also common. Glyphosate, atrazine and pyrasulfotole + bromoxynil remained effective on most R. raphanistrum populations. These results demonstrate that resistance to some herbicides has increased significantly since 2003 when the values were 54% for chlorsulfuron and 60% for 2,4-D therefore, a wide range of weed management options that target all phases of the cropping program are needed to sustain these cropping systems in the future.
Potential for Preseason Herbicide Application to Prevent Weed Emergence in the Subsequent Growing Season. 1. Identification and Evaluation of Possible Herbicides
Publisher: Cambridge University Press (CUP)
Date: 06-2004
DOI: 10.1614/WT-03-13R1
Abstract: The earliest possible seeding of wheat crops in the southern Australian dryland cropping zone is prevented by the lack of a weed control practice that adequately controls initial weed seedling emergence at the start of the growing season. The objective of this study was to determine the potential for using residual herbicides applied up to 1 mo before the start of the growing season to control rigid ryegrass seedlings that emerge after the season-opening rains. In a series of glasshouse studies, S-metolachlor and propyzamide were found to effectively persist on the soil surface through prolonged exposure to hot, dry, and intense sunlight conditions, preventing the establishment of rigid ryegrass seedlings. In addition, these herbicides caused little or no effect on subsequently seeded wheat. It also was determined that S-metolachlor had the potential to retain efficacy on rigid ryegrass seedlings after 12 wk of exposure on the soil surface to these conditions. These studies have identified two herbicides with the potential for use at the novel application timing, i.e., before the commencement of the growing season, in Mediterranean climates of southern Australia.
Effect of Photoinhibitory Treatments on the Activity of Light-Activated Enzymes of C3 and C4 Photosynthetic Carbon Metabolism
Publisher: Oxford University Press (OUP)
Date: 02-1982
DOI: 10.1104/PP.69.2.371
Physiological and Molecular Characterization of Atrazine Resistance in a Wild Radish (Raphanus raphanistrum) Population
Publisher: Cambridge University Press (CUP)
Date: 12-2007
DOI: 10.1614/WT-07-008.1
Abstract: This study documents the physiology and genetics of evolved atrazine resistance in a wild radish population from Western Australia. Plant response to atrazine treatment confirmed a high level of resistance in population WARR5. At 0.25 kg atrazine/ha, all plants from a susceptible population were killed, whereas resistant WARR5 was unaffected at the highest dose tested (4 kg atrazine/ha). Leaf photosynthesis in susceptible plants was inhibited after 1 kg atrazine/ha treatment, whereas leaf photosynthesis in WARR5 plants was unaffected. Furthermore, atrazine resistance was maternally inherited. Sequencing of a psbA gene fragment in resistant WARR5 and susceptible plants revealed a single point mutation resulting in a coding change from Ser 264 to Gly of the D1 protein in resistant plants. We are confident that this mutation is the basis of resistance to the photosystem II inhibitors in this wild radish population.
Tolerance to acetolactate synthase and acetyl-coenzyme A carboxylase inhibiting herbicides in Vulpia bromoides is conferred by two co-existing resistance mechanisms
Publisher: No publisher found
Date: 2004
Contrasting plant ecological benefits endowed by naturally occurring EPSPS resistance mutations under glyphosate selection
Publisher: Wiley
Date: 29-03-2021
DOI: 10.1111/EVA.13230
Abstract: Concurrent natural evolution of glyphosate resistance single‐ and double‐point EPSPS mutations in weed species provides an opportunity for the estimation of resistance fitness benefits and prediction of equilibrium resistance frequencies in environments under glyphosate selection. Assessment of glyphosate resistance benefit was conducted for the most commonly identified single Pro‐106‐Ser and less‐frequent double TIPS mutations in the EPSPS gene evolved in the global damaging weed Eleusine indica . Under glyphosate selection at the field dose, plants with the single Pro‐106‐Ser mutation at homozygous state (P106S‐rr) showed reduced survival and compromised vegetative growth and fecundity compared with TIPS plants. Whereas both homozygous (TIPS‐RR) and compound heterozygous (TIPS‐Rr) plants with the double TIPS resistance mutation displayed similar survival rates when exposed to glyphosate, a significantly higher fecundity in the currency of seed number was observed in TIPS‐Rr than TIPS‐RR plants. The highest plant fitness benefit was associated with the heterozygous TIPS‐Rr mutation, whereas plants with the homozygous Pro‐106‐Ser and TIPS mutations exhibited, respectively, 31% and 39% of the fitness benefit revealed by the TIPS‐Rr plants. Populations are predicted to reach stable allelic and genotypic frequencies after 20 years of glyphosate selection at which the WT allele is lost and the stable genotypic polymorphism is comprised by 2% of heterozygous TIPS‐Rr, 52% of homozygous TIPS‐RR and 46% of homozygous P106S‐rr. The high inbreeding nature of E . indica is responsible for the expected frequency decrease in the fittest TIPS‐Rr in favour of the homozygous TIPS‐RR and P106S‐rr. Mutated alleles associated with the glyphosate resistance EPSPS single EPSPS Pro‐106‐Ser and double TIPS mutations confer contrasting fitness benefits to E . indica under glyphosate treatment and therefore are expected to exhibit contrasting evolution rates in cropping systems under recurrent glyphosate selection.
Glyphosate Resistance in Tridax procumbens via a Novel EPSPS Thr-102-Ser Substitution
Publisher: American Chemical Society (ACS)
Date: 09-07-2018
Abstract: This study confirmed the first case of glyphosate resistance in Tridax procumbens and investigated the glyphosate-resistance mechanisms. Sequencing and cloning of the full 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) coding sequences revealed a point mutation (ACC to TCC) at amino acid position 102, resulting in a novel Thr-102-Ser substitution. Other possible resistance mechanisms (i.e., target-site EPSPS-gene overexpression, nontarget-site differential glyphosate uptake and translocation) were also examined and were unlikely to be involved in resistance in this population. Structural modeling of the wild-type and mutant EPSPS in complex with glyphosate and phosphoenolpyruvate (PEP) revealed that the Thr-102-Ser substitution weakly decreased EPSPS affinity to glyphosate, but sharply increased EPSPS affinity to the natural substrate, PEP. Therefore, this novel mutation is very likely responsible for the observed glyphosate resistance in this tetraploid weed species via dual mechanisms of reducing glyphosate binding and favoring PEP binding to EPSPS.
Pyroxasulfone resistance in Lolium rigidum is metabolism-based
Publisher: Elsevier BV
Date: 06-2018
DOI: 10.1016/J.PESTBP.2018.03.017
Abstract: The evolution of resistant weed populations in response to intensive herbicide selection pressure is a global issue. Resistance to post-emergence herbicides is widespread, whereas soil-applied pre-emergence herbicides can often remain effective. For ex le, in Australia pyroxasulfone is a new pre-emergence soil-applied herbicide which provides control of Lolium rigidum populations resistant to multiple post-emergence herbicide modes of action. A fundamental knowledge of the genetic basis of metabolic resistance in weeds is important for understanding plant evolution pathways under herbicide selection and sustaining long-term weed resistance management. In this study we define the mechanistic basis of resistance to pyroxasulfone in a L. rigidum population. TLC provides evidence that pyroxasulfone resistance is metabolism-based with approximately 88% of parental [
Tumbleweeds in the Western Australian cropping system: seed dispersal characteristics of Salsola australis
Publisher: Wiley
Date: 29-08-2007
Frequency and distribution of herbicide resistance in Raphanus raphanistrum populations randomly collected across the Western Australian wheatbelt
Publisher: Wiley
Date: 06-11-2007
Synergistic Effects of Atrazine and Mesotrione on Susceptible and Resistant Wild Radish (Raphanus raphanistrum) Populations and the Potential for Overcoming Resistance to Triazine Herbicides
Publisher: Cambridge University Press (CUP)
Date: 06-2012
Abstract: The synergistic interaction between mesotrione, a hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide, and atrazine, a photosystem II (PS II)-inhibiting herbicide, has been identified in the control of several weed species. A series of dose–response studies examined the synergistic effect of these herbicides on a susceptible (S) wild radish population. The potential for this interaction to overcome target-site psb A gene-based atrazine resistance in a resistant (R) wild radish population was also investigated. Control of S wild radish with atrazine was enhanced by up to 40% when low rates (1.0 to 1.5 g ha −1 ) of mesotrione were applied in combination. This synergistic response was demonstrated across a range of atrazine–mesotrione rate combinations on this S wild radish population. Further, the efficacy of 1.5 g ha −1 mesotrione increased control of the R population by a further 60% when applied in combination with 400 g ha −1 of atrazine. This result clearly demonstrated the synergistic interaction of these herbicides in overcoming the target-site resistance mechanism. The mechanism responsible for the observed synergistic interaction between mesotrione and atrazine remains unknown. However, it is speculated that an alternate atrazine binding site may be responsible. Regardless of the biochemical nature of this interaction, evidence from whole-plant bioassays clearly demonstrated that synergistic herbicide combinations improve herbicide efficiency, with lower application rates required to control weed populations. This, combined with the potential to overcome psb A gene-based triazine resistance, and, thereby, regain the use of these herbicides, will result in more sustainable herbicide use.
Molecular Bases for Sensitivity to Acetyl-Coenzyme A Carboxylase Inhibitors in Black-Grass
Publisher: Oxford University Press (OUP)
Date: 03-2005
Abstract: In grasses, residues homologous to residues Ile-1,781 and Ile-2,041 in the carboxyl-transferase (CT) domain of the chloroplastic acetyl-coenzyme A (CoA) carboxylase (ACCase) from the grass weed black-grass (Alopecurus myosuroides [Huds.]) are critical determinants for sensitivity to two classes of ACCase inhibitors, aryloxyphenoxypropionates (APPs) and cyclohexanediones. Using natural mutants of black-grass, we demonstrated through a molecular, biological, and biochemical approach that residues Trp-2,027, Asp-2,078, and Gly-2,096 are also involved in sensitivity to ACCase inhibitors. In addition, residues Trp-2,027 and Asp-2,078 are very likely involved in CT activity. Using three-dimensional modeling, we found that the side chains of the five residues are adjacent, located at the surface of the inside of the cavity of the CT active site, in the vicinity of the binding site for APPs. Residues 1,781 and 2,078 are involved in sensitivity to both APPs and cyclohexanediones, whereas residues 2,027, 2,041, and 2,096 are involved in sensitivity to APPs only. This suggests that the binding sites for these two classes of compounds are overlapping, although distinct. Comparison of three-dimensional models for black-grass wild-type and mutant CTs and for CTs from organisms with contrasted sensitivity to ACCase inhibitors suggested that inhibitors fitting into the cavity of the CT active site of the chloroplastic ACCase from grasses to reach their active sites may be tight. The three-dimensional shape of this cavity is thus likely of high importance for the efficacy of ACCase inhibitors.
Exploring the Potential for a Regulatory Change to Encourage Diversity in Herbicide Use
Publisher: Cambridge University Press (CUP)
Date: 09-2016
Abstract: An overreliance on herbicides in several important grain- and cotton-producing regions of the world has led to the widespread evolution of herbicide-resistant weed populations. Of particular concern are weed populations that exhibit simultaneous resistance to multiple herbicides (MHR). Too often, herbicides are the only tool used for weed control. We use the term herbicide-only syndrome (HOS) for this quasi-addiction to herbicides. Growers and their advisers focus on herbicide technology, unaware of or ignoring basic evolutionary principles or the necessary ersity provided by other methods of weed control. Diversity in weed control practices disrupts resistance evolution. Significant challenges exist to implementing ersity, including how to address information so that producers choose to alter existing behaviors (HOS) and take calculated risks by attempting new and more complex strategies. Herbicide resistance management in the long term will require creativity in many sectors, including roles for growers, industry, researchers, consultants, retailers, and regulators. There can be creativity in herbicide registration and regulation, as exemplified by the recent U.S. Environmental Protection Agency program that encourages herbicide registrants to register products in minor crops. We propose one idea for a regulatory incentive to enable herbicide registrants in jurisdictions such as the United States to receive an extended data exclusivity period in exchange for not developing one new herbicide in multiple crops used together in rotation, or for implementing stewardship practices such as robust mixtures or limitations on application frequency. This incentive would provide a mechanism to register herbicides in ways that help to ensure herbicide longevity. Approaches based only on market or financial incentives have contributed to the current situation of widespread MHR. Our suggestion for regulatory creativity is one way to provide both financial and biological benefits to the registering company and to the overall stakeholder community by incentivizing good resistance management.
The economic value of glyphosate-resistant canola in the management of two widespread crop weeds in a Western Australian farming system
Publisher: Elsevier BV
Date: 06-2005
Mechanisms of resistance to acetyl-coenzyme A carboxylase-inhibiting herbicides in aHordeum leporinum population
Publisher: Wiley
Date: 2000
DOI: 10.1002/(SICI)1526-4998(200005)56:5<441::AID-PS159>3.0.CO;2-L
Would you like to sample'l Robot engagement in a shopping centre
Publisher: IEEE
Date: 08-2017
Inheritance of evolved resistance to a novel herbicide (pyroxasulfone)
Publisher: Elsevier BV
Date: 03-2014
DOI: 10.1016/J.PLANTSCI.2013.12.005
Abstract: Agricultural weeds have rapidly adapted to intensive herbicide selection and resistance to herbicides has evolved within ecological timescales. Yet, the genetic basis of broad-spectrum generalist herbicide resistance is largely unknown. This study aims to determine the genetic control of non-target-site herbicide resistance trait(s) that rapidly evolved under recurrent selection of the novel lipid biosynthesis inhibitor pyroxasulfone in Lolium rigidum. The phenotypic segregation of pyroxasulfone resistance in parental, F1 and back-cross (BC) families was assessed in plants exposed to a gradient of pyroxasulfone doses. The inheritance of resistance to chemically dissimilar herbicides (cross-resistance) was also evaluated. Evolved resistance to the novel selective agent (pyroxasulfone) is explained by Mendelian segregation of one semi-dominant allele incrementally herbicide-selected at higher frequency in the progeny. In BC families, cross-resistance is conferred by an incompletely dominant single major locus. This study confirms that herbicide resistance can rapidly evolve to any novel selective herbicide agents by continuous and repeated herbicide use. The results imply that the combination of herbicide options (rotation, mixtures or combinations) to exploit incomplete dominance can provide acceptable control of broad-spectrum generalist resistance-endowing monogenic traits. Herbicide ersity within a set of integrated management tactics can be one important component to reduce the herbicide selection intensity.
Phorate can reverse P450 metabolism-based herbicide resistance inLolium rigidum
Publisher: Wiley
Date: 17-11-2016
DOI: 10.1002/PS.4441
Abstract: Organophosphate insecticides can inhibit specific cytochrome P450 enzymes involved in metabolic herbicide resistance mechanisms, leading to synergistic interactions between the insecticide and the herbicide. In this study we report synergistic versus antagonistic interactions between the organophosphate insecticide phorate and five different herbicides observed in a population of multiple herbicide-resistant Lolium rigidum. Phorate synergised with three different herbicide modes of action, enhancing the activity of the ALS inhibitor chlorsulfuron (60% LD We report the selective reversal of P450-mediated metabolic multiple resistance to chlorsulfuron and trifluralin in the grass weed L. rigidum by synergistic interaction with the insecticide phorate, and discuss the putative mechanistic basis. This research should encourage ersity in herbicide use patterns for weed control as part of a long-term integrated management effort to reduce the risk of selection of metabolism-based multiple herbicide resistance in L. rigidum. © 2016 Society of Chemical Industry.
Diversity of Acetyl-Coenzyme A Carboxylase Mutations in Resistant Lolium Populations: Evaluation Using Clethodim
Publisher: Oxford University Press (OUP)
Date: 24-08-2007
Cross-Resistance to Herbicides in Annual Ryegrass (Lolium rigidum)
Publisher: Oxford University Press (OUP)
Date: 11-1991
DOI: 10.1104/PP.97.3.1026
Rotations and mixtures of soil‐applied herbicides delay resistance
Publisher: Wiley
Date: 27-07-2019
DOI: 10.1002/PS.5534
Abstract: Weed resistance to foliar herbicides has dramatically increased worldwide in the last two decades. As a consequence, current practices of weed management have changed, with an increased adoption of soil-applied herbicides to restore control of herbicide-resistant weeds. We foresee metabolism-based resistance and cross-resistance to soil-applied herbicides as a potential global consequence to the increased and widespread adoption of new and old soil-applied herbicides. Thus, the aim of this study is to use computer simulation modelling to quantify and rank the risk of weeds evolving resistance to soil-applied herbicides under different usage strategies (single herbicide use, rotations and mixtures) and population genetic hypotheses. Simulations indicate that without rotation it takes twice as long to select for resistance to a particular soil-applied herbicide - trifluralin - than to any other herbicide option considered. Relative to trifluralin-only use, simple herbicide rotation patterns have no effect in delaying resistance, whereas more complex rotation patterns can delay resistance two- or three-fold. Herbicide mixtures further delay resistance up to six-fold in comparison to single use or simple herbicide rotations. By computer modelling simulations we demonstrate that mixtures maximize herbicide effectiveness and the selection heterogeneity of soil-applied herbicides, and delay herbicide resistance evolution in weedy plants. Our study is consistent with previous state-of-art scientific evidence (i.e. epidemiological and modelling studies across different systems and pests) and extension efforts (i.e. 'rotate herbicide mixtures') to provide insight to manage the selection and evolution of weed resistance. © 2019 Society of Chemical Industry.
Reduced paraquat translocation in paraquat resistant Arctotheca calendula (L.) Levyns is a consequence of the primary resistance mechanism, not the cause
Publisher: Elsevier BV
Date: 07-2003
Evolution of resistance to HPPD‐inhibiting herbicides in a wild radish population via enhanced herbicide metabolism
Publisher: Wiley
Date: 03-01-2020
DOI: 10.1002/PS.5725
Abstract: Relatively new herbicides that target 4-hydroxyphenylpyruvate dioxygenase (HPPD) are now available for use on the world's great grain crops (rice, wheat, corn and soybean) and for other uses. With widespread and persistent use of HPPD-inhibiting herbicides, the evolution of HPPD-inhibiting herbicide resistant weeds is inevitable. Currently, resistance to HPPD-inhibiting herbicides is known in two weed species, waterhemp and Palmer amaranth. Here, we report a HPPD-inhibiting herbicide resistant wild radish population from the Western Australia grain belt. This population was not selected with HPPD-inhibiting herbicides, rather it evolved resistance to earlier used herbicides with different modes of action and exhibits cross-resistance to HPPD-inhibiting herbicides. Dose-response experiments showed the resistant (R) population exhibits 4 to 6.5-fold resistance to the HPPD-inhibiting herbicides mesotrione, tembotrione and isoxaflutole, compared to the susceptible (S) population. This resistance is not target-site based as cloning of full coding sequences of the HPPD genes from S and R plants did not reveal resistance-endowing single nucleotide polymorphisms. The HPPD gene expression levels are similar in S and R plants. In addition, no differences in [ We confirm resistance to HPPD-inhibiting herbicides exists in a population of the economically damaging global weed wild radish. The resistance in this population is due to a non-target-site based enhanced rate of herbicide metabolism. © 2019 Society of Chemical Industry.
Detecting karrikinolide responses in seeds of the Poaceae
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/BT11170
Abstract: The smoke-derived chemical karrikinolide commonly triggers seeds in the Brassicaceae, Solanaceae and Asteraceae families to germinate, yet species in the Poaceae – another major understorey and weed family – have responded to the chemical with mixed results. This study aimed to understand why some grass species respond to karrikinolide while others do not. Using a field-based seed-burial trial, dose-response experiment, and stratification experiment, we investigated whether karrikinolide could alleviate dormancy and trigger seeds to germinate for seven global agronomic weeds: Avena fatua L., Lolium rigidum Gaudin, Eragrostis curvula (Schrad.) Nees, Phalaris minor Retz., Hordeum glaucum Steud., Ehrharta calycina Sm. and Bromus diandrus Roth. Seeds of A. fatua were consistently stimulated to germinate with karrikinolide in all experiments, whether seeds were freshly collected or dormancy had been partially alleviated. In contrast, seeds of L. rigidum failed to respond to karrikinolide when the seeds were fresh, after-ripened in the laboratory, and even during natural dormancy loss in the field. Interestingly, although karrikinolide did not stimulate freshly collected E. curvula seeds to germinate, it hastened dormancy loss when applied during stratification. These findings are helpful for understanding the responses of grass species following fire. They also contribute to a growing body of research aimed at using karrikinolide as a tool for triggering uniform germination of seeds for enhancing restoration efforts and depleting the weed seed bank.
Iterated belief revision and dalal⇔s operator
Publisher: ACM
Date: 09-07-2018
Bon Appetit! Robot Persuasion for Food Recommendation
Publisher: ACM
Date: 03-2018
Reduced sensitivity to paraquat evolves under selection with low glyphosate doses in Lolium rigidum
Publisher: Springer Science and Business Media LLC
Date: 15-02-2011
Maps in multiple belief change
Publisher: Association for Computing Machinery (ACM)
Date: 10-2012
Abstract: Multiple Belief Change extends the classical AGM framework for Belief Revision introduced by Alchourron, Gardenfors, and Makinson in the early ’80s. The extended framework includes epistemic input represented as a (possibly infinite) set of sentences , as opposed to a single sentence assumed in the original framework. The transition from single to multiple epistemic input worked out well for the operation of belief revision. The AGM postulates and the system-of-spheres model were adequately generalized and so was the representation result connecting the two. In the case of belief contraction however, the transition was not as smooth. The generalized postulates for contraction, which were shown to correspond precisely to the generalized partial meet model , failed to match up to the generalized epistemic entrenchment model . The mismatch was fixed with the addition of an extra postulate, called the limit postulate , that relates contraction by multiple epistemic input to a series of contractions by single epistemic input. The new postulate however creates problems on other fronts. First, the limit postulate needs to be mapped into appropriate constraints in the partial meet model. Second, via the Levi and Harper Identities, the new postulate translates into an extra postulate for multiple revision, which in turn needs to be characterized in terms of systems of spheres. Both these open problems are addressed in this article. In addition, the limit postulate is compared with a similar condition in the literature, called (K*F), and is shown to be strictly weaker than it. An interesting aspect of our results is that they reveal a profound connection between rationality in multiple belief change and the notion of an elementary set of possible worlds (closely related to the notion of an elementary class of models from classical logic).
Evolved Resistance to Glyphosate in Junglerice (Echinochloa colona) from the Tropical Ord River Region in Australia
Publisher: Cambridge University Press (CUP)
Date: 09-2012
Abstract: The objective of this study was to determine whether a junglerice population from the tropical Ord River region of northwest Australia was glyphosate resistant, and whether alternative herbicides labeled for junglerice control were still effective. Seed s les collected from the field site were initially screened with glyphosate in the glasshouse, and surviving in iduals were self-pollinated for subsequent glyphosate dose-response studies. Glyphosate resistance was confirmed, as the suspected resistant population was found to be 8.6-fold more resistant to glyphosate than a susceptible population based on survival (LD 50 of 3.72 kg ha −1 ), and 5.6-fold more resistant based on biomass reduction (GR 50 of 1.16 kg ha −1 ). The glyphosate-resistant population was susceptible to label-recommended doses of all other herbicides assessed, including three acetyl-CoA carboxylase (ACC) –inhibiting herbicides (fluazifop-P, haloxyfop, and sethoxydim), two acetolactate synthase (ALS) –inhibiting herbicides (imazamox and sulfometuron), paraquat, and glufosinate. Glyphosate resistance has previously evolved in numerous species found in glyphosate-resistant cropping systems, no-till chemical fallow, fence line, and perennial crop situations. Here we report the evolution of glyphosate resistance in a cropping system that included annual tillage. The evolution of glyphosate resistance in junglerice from a tropical cropping system further demonstrates the need for improved glyphosate stewardship practices globally.
Paraquat resistance in a Lolium rigidum population is governed by one major nuclear gene
Publisher: Springer Science and Business Media LLC
Date: 24-03-2009
DOI: 10.1007/S00122-009-1008-3
Abstract: Paraquat resistance in an annual ryegrass (Lolium rigidum Gaud.) population (AFLR1) has been attributed to reduced paraquat translocation. Genetic inheritance of paraquat resistance in this population was investigated in the present study. The paraquat dose response of progeny from 8 F(1) families was more similar to that of the resistant than the susceptible parent, while the equivalent data for a further three families were intermediate compared to those of the parental populations. No significant differences in dose response were observed between reciprocal crosses of specific F(1) families. These results suggest that paraquat resistance in AFLR1 is inherited as a dominant or partially dominant nuclear-encoded trait. Pseudo-F(2) (psi-F(2)) generation seedlings were treated with multiple dose rates sufficient to control the susceptible parental population, and observed segregation ratios in all instances conformed to a 3:1 (resistant:susceptible) segregation ratio, and this ratio was further confirmed by in idual phenotyping of cloned plant genotypes. A single major nuclear gene is hence apparently responsible for evolved paraquat resistance in AFLR1.
Growth and competitiveness of paraquat‐resistant and ‐susceptible biotypes of Hordeum leporinum
Publisher: Wiley
Date: 08-1996
Differential translocation of paraquat in paraquat‐resistant populations of Hordeum leporinum
Publisher: Wiley
Date: 08-07-2005
Combined effects of wheat competition and 2,4‐D amine on phenoxy herbicide resistant Raphanus raphanistrum populations
Publisher: Wiley
Date: 18-05-2009
Plasma membrane receptor-like kinases and transporters are associated with 2,4-D resistance in wild radish
Publisher: Oxford University Press (OUP)
Date: 24-10-2019
DOI: 10.1093/AOB/MCZ173
Abstract: Resistance to the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) in wild radish (Raphanus raphanistrum) appears to be due to a complex, multifaceted mechanism possibly involving enhanced constitutive plant defence and alterations in auxin signalling. Based on a previous gene expression analysis highlighting the plasma membrane as being important for 2,4-D resistance, this study aimed to identify the components of the leaf plasma membrane proteome that contribute to resistance. Isobaric tagging of peptides was used to compare the plasma membrane proteomes of a 2,4-D-susceptible and a 2,4-D-resistant wild radish population under control and 2,4-D-treated conditions. Eight differentially abundant proteins were then targeted for quantification in the plasma membranes of 13 wild radish populations (two susceptible, 11 resistant) using multiple reaction monitoring. Two receptor-like kinases of unknown function (L-type lectin domain-containing receptor kinase IV.1-like and At1g51820-like) and the ATP-binding cassette transporter ABCB19, an auxin efflux transporter, were identified as being associated with auxinic herbicide resistance. The variability between wild radish populations suggests that the relative contributions of these candidates are different in the different populations. To date, no receptor-like kinases have been reported to play a role in 2,4-D resistance. The lectin-domain-containing kinase may be involved in perception of 2,4-D at the plasma membrane, but its ability to bind 2,4-D and the identity of its signalling partner(s) need to be confirmed experimentally. ABCB19 is known to export auxinic compounds, but its role in 2,4-D resistance in wild radish appears to be relatively minor.
Towards large-scale prediction of Lolium rigidum emergence. II. Correlation between dormancy and herbicide resistance levels suggests an impact of cropping systems
Publisher: Wiley
Date: 08-12-2011
ALS herbicide resistance mutations in Raphanus raphanistrum: evaluation of pleiotropic effects on vegetative growth and ALS activity
Publisher: Wiley
Date: 24-10-2012
DOI: 10.1002/PS.3419
Abstract: Gene mutations that endow herbicide resistance may cause pleiotropic effects on plant ecology and physiology. This paper reports on the effect of a number of known and novel target-site resistance mutations of the ALS gene (Ala-122-Tyr, Pro-197-Ser, Asp-376-Glu or Trp-574-Leu) on vegetative growth traits of the weed Raphanus raphanistrum. The results from a series of experiments have indicated that none of these ALS resistance mutations imposes negative pleiotropic effects on relative growth rate (RGR), photosynthesis and resource-competitive ability in R. raphanistrum plants. The absence of pleiotropic effects on plant growth occurs in spite of increased (Ala-122-Tyr, Pro-197-Ser, Asp-376-Glu) and decreased (Trp-574-Leu) extractable ALS activity. The absence of detrimental pleiotropic effects on plant growth associated with the ALS target-site resistance mutations reported here is a contributing factor in resistance alleles being at relatively high frequencies in ALS-herbicide-unselected R. raphanistrum populations.
Why was resistance to shorter‐acting pre‐emergence herbicides slower to evolve?
Publisher: Wiley
Date: 20-02-2017
DOI: 10.1002/PS.4509
Abstract: Across several agricultural systems the evolution of herbicide resistance has occurred more rapidly to post-emergence than pre-emergence herbicides however, the reasons for this are not clear. We used a new simulation model to investigate whether interactions between differences in order of application and weed cohorts affected could explain this historically observed difference between the herbicide groups. A 10 year delay in resistance evolution was predicted for a shorter-acting residual pre-emergence (cf. post-emergence), when all other parameters were identical. Differences in order of application between pre- and post-emergence herbicides had minimal effect on rates of resistance evolution when similar weed cohorts were affected. This modelling suggested that the historically observed lower levels of resistance to pre-emergence herbicides are most likely to be due to the smaller number of weed cohorts affected by many pre-emergence herbicides. The lower number of weed cohorts affected by pre-emergence herbicides necessitated the use of additional, effective control measures, thereby reducing resistance evolution. This study highlights the advantages of applying multiple control measures to each weed cohort. © 2016 Society of Chemical Industry.
Distribution and frequency of herbicide-resistant wild oat (Avena spp.) across the Western Australian grain belt
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/CP08178
Abstract: In 2005, a random survey was conducted across 14 million hectares of the Western Australian grain belt to establish the frequency and distribution of herbicide-resistant wild oat (Avena spp.) in cropping fields. In total, 677 cropping fields were visited, with wild oat populations collected from 150 fields. These wild oat populations were screened with several herbicides commonly used to control this weed. Most of the wild oat populations (71%) were found to contain in iduals resistant to the ACCase-inhibiting herbicide diclofop-methyl. Resistance to other ACCase-inhibiting herbicides was markedly lower. Herbicides of alternative modes of action were effective on all wild oat populations. Overall, wild oat resistance to diclofop-methyl was found to be widespread across the Western Australian grain belt, but resistance to other herbicides was relatively low. Therefore, through ersity in herbicide use and with cultural management, it is possible to maintain wild oat populations at a low level and/or minimise herbicide resistance evolution.
Multiple-herbicide resistance across four modes of action in wild radish (Raphanus raphanistrum)
Publisher: Cambridge University Press (CUP)
Date: 02-2004
DOI: 10.1614/WS-03-016R
Abstract: Populations of wild radish were collected from two fields in the northern Western Australian wheatbelt, where typical herbicide-use patterns had been practiced for the previous 17 seasons within an intensive crop production program. The herbicide resistance status of these populations clearly established that there was multiple-herbicide resistance across many herbicides from at least four modes of action. One population exhibited multiple-herbicide resistance to the phytoene desaturase (PDS)–inhibiting herbicide diflufenican (3.0-fold), the auxin analog herbicide 2,4-D (2.2-fold), and the photosystem II–inhibiting herbicides metribuzin and atrazine. Another population was found to be multiply resistant to the acetolactate synthase–inhibiting herbicides, the PDS-inhibiting herbicide diflufenican (2.5-fold), and the auxin analog herbicide 2,4-D amine (2.4-fold). Therefore, each population has developed multiple-herbicide resistance across several modes of action. The multiple resistance status of these wild radish populations developed from conventional herbicide usage in intensive cropping rotations, indicating a dramatic challenge for the future control of wild radish.
Relevance in belief revision
Publisher: Elsevier BV
Date: 12-2015
Genetic inheritance of dinitroaniline resistance in an annual ryegrass population
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.PLANTSCI.2019.02.019
Abstract: The increasing number of weedy species resistant to dinitroaniline herbicides warrants studies on the evolutionary factors contributing to resistance evolution, including genetic inheritance of resistance traits. In this study, we investigated the genetic control of trifluralin resistance in a well-characterised Lolium rigidum Gaud. population from Western Australia. This population was purified to contain plants homozygous for the Val-202-Phe α-tubulin mutation, and used as the resistant (R) parents and crossed with susceptible (S) parents to produce eight reciprocal F1 families. Trifluralin dose response curves of the eight F1 families indicate that trifluralin resistance in this population is inherited as an incomplete recessive nuclear trait. The F1 plants were crossed within each families to establish eight pseudo-F2 (ψ-F2) families. Segregation ratio of resistance and susceptibility in ψ-F2 families were determined using the discriminating trifluralin rates of 120 and 480 g a.i. ha
Distinct non-target site mechanisms endow resistance to glyphosate, ACCase and ALS-inhibiting herbicides in multiple herbicide-resistant Lolium rigidum
Publisher: Springer Science and Business Media LLC
Date: 15-07-2009
DOI: 10.1007/S00425-009-0981-8
Abstract: This study investigates mechanisms of multiple resistance to glyphosate, acetyl-coenzyme A carboxylase (ACCase) and acetolactate synthase (ALS)-inhibiting herbicides in two Lolium rigidum populations from Australia. When treated with glyphosate, susceptible (S) plants accumulated 4- to 6-fold more shikimic acid than resistant (R) plants. The resistant plants did not have the known glyphosate resistance endowing mutation of 5-enolpyruvylshikimate-3 phosphate synthase (EPSPS) at Pro-106, nor was there over-expression of EPSPS in either of the R populations. However, [(14)C]-glyphosate translocation experiments showed that the R plants in both populations have altered glyphosate translocation patterns compared to the S plants. The R plants showed much less glyphosate translocation to untreated young leaves, but more to the treated leaf tip, than did the S plants. Sequencing of the carboxyl transferase domain of the plastidic ACCase gene revealed no resistance endowing amino acid substitutions in the two R populations, and the ALS in vitro inhibition assay demonstrated herbicide-sensitive ALS in the ALS R population (WALR70). By using the cytochrome P450 inhibitor malathion and amitrole with ALS and ACCase herbicides, respectively, we showed that malathion reverses chlorsulfuron resistance and amitrole reverses diclofop resistance in the R population examined. Therefore, we conclude that multiple glyphosate, ACCase and ALS herbicide resistance in the two R populations is due to the presence of distinct non-target site based resistance mechanisms for each herbicide. Glyphosate resistance is due to reduced rates of glyphosate translocation, and resistance to ACCase and ALS herbicides is likely due to enhanced herbicide metabolism involving different cytochrome P450 enzymes.
Ecological fitness of a glyphosate-resistant Lolium rigidum population: Growth and seed production along a competition gradient
Publisher: Elsevier BV
Date: 05-2007
Cytochrome P450 CYP81A10v7 in Lolium rigidum confers metabolic resistance to herbicides across at least five modes of action
Publisher: Wiley
Date: 27-11-2020
DOI: 10.1111/TPJ.15040
Multiple herbicide resistance in a glyphosate-resistant rigid ryegrass (Lolium rigidum) population
Publisher: Cambridge University Press (CUP)
Date: 12-2003
DOI: 10.1614/WS-04-007R1
Abstract: Surviving rigid ryegrass plants were collected from a cropping field at Pindar, Western Australia (population WALR 50), after inadequate control by glyphosate applied at the normal field rate. Plants were grown to maturity in pots and seeds were collected. Glyphosate dose–response experiments with known susceptible and resistant control populations confirmed the resistant status of the WALR 50 population. The glyphosate rate resulting in 5% mortality (LD 50 ) and GR 50 (the glyphosate rate required to reduce mean growth of in iduals to 50% of the untreated control) values for this population were 1,069 and 217 g ae ha −1 , respectively, corresponding to R:S ratios of 3.4 and 1.9 for mortality and growth. In addition, a novel root growth–based assay of glyphosate resistance was developed and validated, giving a root growth GR 50 R:S ratio of 3.4. A resistance profile was established by assessing population-level survival of WALR 50 after applications at recommended rates of a range of herbicides commonly used for rigid ryegrass control in Australia. High levels of resistance to the acetolactate synthase (ALS)–inhibiting sulfonylurea herbicides chlorsulfuron and sulfometuron, moderate resistance to the acetyl coenzyme A carboxylase (ACCase)–inhibiting herbicide diclofop, and low levels of resistance to the imidazilinone herbicide imazethapyr were found. More detailed dose–response experiments confirmed resistance to chlorsulfuron, sulfometuron, and diclofop. In vitro enzyme-inhibition studies demonstrated that ALS resistance in WALR 50 is due to an insensitive target enzyme and that ACCase resistance is due to a nontarget site–based mechanism. WALR 50 is the first glyphosate-resistant weed population with confirmed resistance to ACCase- and ALS-inhibiting herbicides.
Paraquat resistance in a biotype of Vulpia bromoides (L.) S. F. Gray
Publisher: Wiley
Date: 10-1993
Do You Trust Me, Blindly? Factors Influencing Trust Towards a Robot Recommender System
Publisher: IEEE
Date: 08-2018
The frequency of herbicide-resistant wild oat (Avena spp.) populations remains stable in Western Australian cropping fields
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/CP15295
Abstract: Avena is a problematic weed of cropping regions of southern Australia and many areas of the world. In 2010, a random survey was conducted across 14 million hectares of the Western Australian grain belt to monitor the change in herbicide resistance levels by comparing resistance frequency results with a survey conducted in 2005. Screening Avena populations with herbicides commonly used to control this weed revealed that 48% of Avena populations displayed resistance to the commonly used acetyl-Co A carboxylase-inhibiting herbicides, which was lower than that found in 2005 (71%). The broad-spectrum herbicides glyphosate and paraquat provided good control of all Avena populations. Resistance to acetolactate synthase-inhibiting herbicides and to fl rop were detected for the first time in Western Australia in this survey. Therefore, a wide range of weed management options that target all phases of the cropping program are needed to sustain these cropping systems in the future.
Rapid degradation of carbetamide upon repeated application to Australian soils
Publisher: Elsevier BV
Date: 05-2001
Identification of resistance to either paraquat or ALS‐inhibiting herbicides in two Western Australian Hordeum leporinum biotypes
Publisher: Wiley
Date: 30-01-2012
DOI: 10.1002/PS.2323
Abstract: Hordeum populations are becoming increasingly difficult to control in cropping fields. Two herbicide-resistant H. leporinum populations were identified during a random crop survey after herbicides were applied. The study aimed to determine the herbicide resistance profile of these H. leporinum biotypes to a range of herbicides used for their control. Based on dose-response studies, one H. leporinum population was very highly resistant to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) and also displayed low-level resistance to imazamox (an imidazolinone herbicide). Reduced sensitivity of the ALS enzyme was identified with in vitro activity assays. Gene sequence analysis revealed a proline-to-threonine substitution at amino acid position 197 of ALS, which is likely to be the molecular basis for resistance in this population. Herbicide screening also revealed a different H. leporinum population with resistance to the bipyridyl herbicide paraquat. This study established the first cases of (1) sulfonylurea-to-imidazolinone cross-resistance and (2) field-evolved paraquat resistance in a Hordeum species in Western Australia.
Exploring quinclorac resistance mechanisms in Echinochloa crus‐pavonis from China
Publisher: Wiley
Date: 08-08-2020
DOI: 10.1002/PS.6007
Simulating evolution of glyphosate resistance in Lolium rigidum I: population biology of a rare resistance trait
Publisher: Wiley
Date: 18-11-2003
Australian Herbicide Resistance Initiative (AHRI) Celebrates its 20th Anniversary
Publisher: Research Information Ltd.
Date: 06-2019
DOI: 10.1564/V30_JUN_05
Aldo-keto Reductase Metabolizes Glyphosate and Confers Glyphosate Resistance in Echinochloa colona
Publisher: Oxford University Press (OUP)
Date: 24-09-2019
DOI: 10.1104/PP.19.00979
Directional selection for flowering time leads to adaptive evolution in Raphanus raphanistrum (Wild radish)
Publisher: Wiley
Date: 17-02-2016
DOI: 10.1111/EVA.12350
Resistance of dicot weeds to acetolactate synthase (ALS)‐inhibiting herbicides in Australia
Publisher: Wiley
Date: 06-1995
Harvest Weed Seed Control Systems are Similarly Effective on Rigid Ryegrass
Publisher: Cambridge University Press (CUP)
Date: 03-2017
DOI: 10.1017/WET.2017.6
Abstract: Harvest weed seed control (HWSC) systems have been developed to exploit the high proportions of seed retained at maturity by the annual weeds rigid ryegrass, wild radish, bromegrass, and wild oats. To evaluate the efficacy of HWSC systems on rigid ryegrass populations, three systems, the Harrington Seed Destructor (HSD), chaff carts, and narrow-windrow burning were compared at 24 sites across the western and southern wheat production regions of Australia. HWSC treatments were established at harvest (Nov. – Dec.) in wheat crops with low to moderate rigid ryegrass densities (1 to 26 plants m −2 ). Rigid ryegrass counts at the commencement of the next growing season (Apr. – May) determined that HWSC treatments were similarly effective in reducing emergence. Chaff carts, narrow-windrow burning, or HSD systems act similarly on rigid ryegrass seed collected during harvest to deliver substantial reductions in subsequent rigid ryegrass populations by restricting seedbank inputs. On average, population densities were reduced by 60%, but there was considerable variation between sites (37 to 90%) as influenced by seed production and the residual seedbank. Given the observed high rigid ryegrass seed production levels at crop maturity it is clear that HWSC has a vital role in preventing seedbank inputs in Australian conservation cropping systems.
Identification of Triazine-ResistantVulpia bromoides
Publisher: Cambridge University Press (CUP)
Date: 06-2016
Abstract: In Australia, triazine herbicides have routinely controlled the Vulpia species ( Vulpia bromoides , Vulpia myuros , and Vulpia fasciculata collectively referred to as silvergrass). However, a simazine-resistant silvergrass biotype, collected from Pingelly in the Western Australian grain belt in 2014, has been confirmed. Compared to the pooled mortality of three simazine-susceptible silvergrass populations (S1, S2, and S3), the simazine-resistant Pingelly population was 594-fold resistant at the LD 50 level. Dose-response screening of the simazine-selected progeny ( 800 g ai simazine ha −1 ) demonstrated that the simazine resistance mechanism was heritable. Sequencing of the chloroplast psb A gene revealed the resistant population is homozygous for a serine 264 to glycine mutation, which confers a high-level triazine resistance. As expected this Ser-264-Gly mutation conferred resistance to atrazine and metribuzin, but not the phenyl-urea diuron. This is the first published report confirming field-evolved triazine resistance in a Vulpia population.
High Levels of Adoption Indicate That Harvest Weed Seed Control Is Now an Established Weed Control Practice in Australian Cropping
Publisher: Cambridge University Press (CUP)
Date: 10-05-2017
DOI: 10.1017/WET.2017.9
Abstract: HWSC systems that target weed seed production during harvest have been in use in Australian crop production systems for over 30 years. Until recently, though, grower adoption of these systems has been relatively low. It is now apparent with the introduction of a range of new weed seed targeting systems that there is renewed grower interest in the use of this approach to weed control. With the aim of determining the current adoption and use of HWSC systems, 600 crop producers from throughout Australia’s cropping regions were interviewed on their adoption and use of these systems. This survey established that 43% of Australian growers are now routinely using HWSC to target weed seed production during grain harvest. The adoption of narrow-windrow burning (30%) was considerably greater than the other currently available techniques of chaff tramlining (7%), chaff carts (3%), bale-direct system (3%), and the Harrington Seed Destructor (HSD) ( %). When growers were asked about their future use of these systems 82% indicated that they would be using some form of HWSC within five years. Grower preferences for future HWSC use were primarily for either narrow-windrow burning (42%) or the HSD (29%). This very high level of current and potential HWSC adoption signifies that HWSC is now considered an established weed control practice by Australian growers.
The molecular bases for resistance to acetyl co-enzyme A carboxylase (ACCase) inhibiting herbicides in two target-based resistant biotypes of annual ryegrass (Lolium rigidum)
Publisher: Springer Science and Business Media LLC
Date: 23-08-2005
DOI: 10.1007/S00425-005-0095-X
Abstract: Acetyl-CoA carboxylase (ACCase) (EC.6.4.1.2) is an essential enzyme in fatty acid biosynthesis and, in world agriculture, commercial herbicides target this enzyme in plant species. In nearly all grass species the plastidic ACCase is strongly inhibited by commercial ACCase inhibiting herbicides [aryloxyphenoxypropionate (APP) and cyclohexanedione (CHD) herbicide chemicals]. Many ACCase herbicide resistant biotypes (populations) of L. rigidum have evolved, especially in Australia. In many cases, resistance to ACCase inhibiting herbicides is due to a resistant ACCase enzyme. Two ACCase herbicide resistant L. rigidum biotypes were studied to identify the molecular basis of ACCase inhibiting herbicide resistance. The carboxyl-transferase (CT) domain of the plastidic ACCase gene was lified by PCR and sequenced. Amino acid substitutions in the CT domain were identified by comparison of sequences from resistant and susceptible plants. The amino acid residues Gln-102 (CAG codon) and Ile-127 (ATA codon) were substituted with a Glu residue (GAG codon) and Leu residue (TTA codon), respectively, in both resistant biotypes. Amino acid positions 102 and 127 within the fragment sequenced from L. rigidum corresponded to amino acid residues 1756 and 1781, respectively, in the A. myosuroides full ACCase sequence. Allele-specific PCR results further confirmed the mutations linked with resistance in these populations. The Ile-to-Leu substitution at position 1781 has been identified in other resistant grass species as endowing resistance to APP and CHD herbicides. The Gln-to-Glu substitution at position 1756 has not previously been reported and its role in herbicide resistance remains to be established.
Targeting Weed Seeds In-Crop: A New Weed Control Paradigm for Global Agriculture
Publisher: Cambridge University Press (CUP)
Date: 09-2013
Abstract: The widespread evolution of multiple herbicide resistance in the most serious annual weeds infesting Australian cropping fields has forced the development of alternative, non-chemical weed control strategies, especially new techniques at grain harvest. Harvest weed seed control (HWSC) systems target weed seed during commercial grain harvest operations and act to minimize fresh seed inputs to the seedbank. These systems exploit two key biological weaknesses of targeted annual weed species: seed retention at maturity and a short-lived seedbank. HWSC systems, including chaff carts, narrow windrow burning, bale direct, and the Harrington Seed Destructor, target the weed seed bearing chaff material during commercial grain harvest. The destruction of these weed seeds at or after grain harvest facilitates weed seedbank decline, and when combined with conventional herbicide use, can drive weed populations to very low levels. Very low weed populations are key to sustainability of weed control practices. Here we introduce HWSC as a new paradigm for global agriculture and discuss how these techniques have aided Australian grain cropping and their potential utility in global agriculture.
Recurrent Sublethal-Dose Selection for Reduced Susceptibility of Palmer Amaranth (Amaranthus palmeri) to Dicamba
Publisher: Cambridge University Press (CUP)
Date: 23-01-2017
DOI: 10.1017/WSC.2016.27
Abstract: The management of glyphosate-resistant Palmer amaranth has been a challenge in southern United States cropping systems. Registration of dicamba-resistant crops will provide an alternative management option to control herbicide-resistant Palmer amaranth populations, particularly those having resistance to herbicide Groups 2, 3, 5, 9, 14, and 27. However, repeated use of sublethal doses of dicamba may lead to rapid evolution of herbicide resistance, especially in Palmer amaranth—a species with a strong tendency to evolve resistance. Therefore, selection experiments with dicamba were conducted on Palmer amaranth using sublethal doses. In the greenhouse, a known susceptible Palmer amaranth population was subjected to sublethal dicamba doses for three generations (P 1 –P 3 ). Susceptibility of the in iduals to dicamba was evaluated, and its susceptibility to 2,4-D was characterized. Based on the greenhouse study, following three generations of dicamba selection, the dose required to cause 50% mortality increased from 111 g ae ha −1 for parental in iduals (P 0 ) to 309 g ae ha −1 for the P 3 . Furthermore, reduced susceptibility of the P 3 to 2,4-D was also evident. This research presents the first evidence that recurrent use of sublethal dicamba doses can lead to reduced susceptibility of Palmer amaranth to dicamba as well as 2,4-D. Here, we show that selection from sublethal dicamba doses has an important role in rapid evolution of Palmer amaranth with reduced susceptibility to auxin-type herbicides.
Fitness costs associated with evolved herbicide resistance alleles in plants
Publisher: Wiley
Date: 13-10-2009
DOI: 10.1111/J.1469-8137.2009.03055.X
Abstract: Predictions based on evolutionary theory suggest that the adaptive value of evolved herbicide resistance alleles may be compromised by the existence of fitness costs. There have been many studies quantifying the fitness costs associated with novel herbicide resistance alleles, reflecting the importance of fitness costs in determining the evolutionary dynamics of resistance. However, many of these studies have incorrectly defined resistance or used inappropriate plant material and methods to measure fitness. This review has two major objectives. First, to propose a methodological framework that establishes experimental criteria to unequivocally evaluate fitness costs. Second, to present a comprehensive analysis of the literature on fitness costs associated with herbicide resistance alleles. This analysis reveals unquestionable evidence that some herbicide resistance alleles are associated with pleiotropic effects that result in plant fitness costs. Observed costs are evident from herbicide resistance‐endowing amino acid substitutions in proteins involved in amino acid, fatty acid, auxin and cellulose biosynthesis, as well as enzymes involved in herbicide metabolism. However, these resistance fitness costs are not universal and their expression depends on particular plant alleles and mutations. The findings of this review are discussed within the context of the plant defence trade‐off theory and herbicide resistance evolution. Contents Summary 751 I. Introduction 752 II. Methods for the detection and estimation of herbicide resistance fitness costs 753 III. Fitness costs associated with AHAS target site resistance 756 IV. Fitness costs associated with ACCase target site resistance 757 V. Fitness costs associated with resistance to phenoxy herbicides 758 VI. Arabidopsis thaliana as a model plant to understand pleiotropic effects of herbicide target‐site based resistance alleles 759 VII. Fitness costs associated with herbicide resistance endowed by enhanced rates of herbicide metabolism catalysed by P450 enzymes 760 VIII. Fitness costs associated with glyphosate resistance 760 IX. Discussion 761 X. Conclusion 762 Acknowledgements 763 References 763
Triazine Resistance in a Biotype of Wild Radish (Raphanus raphanistrum) in Australia1
Publisher: Cambridge University Press (CUP)
Date: 10-2001
Interaction between light and chilling temperature on the inhibition of photosynthesis in chilling‐sensitive plants*
Publisher: Wiley
Date: 03-1983
Can herbicide safeners allow selective control of weedy rice infesting rice crops?
Publisher: Wiley
Date: 19-09-2017
DOI: 10.1002/PS.4411
Abstract: Rice is a major field crop of paramount importance for global food security. However, the increased adoption of more profitable and resource-efficient direct-seeded rice (DSR) systems has contributed to greater weed infestations, including weedy rice, which has become a severe problem in several Asian regions. In this study we have developed a conceptually novel method to protect rice plants at high doses of clomazone and triallate. The insecticide phorate applied to rice seeds provided a substantial level of protection against the herbicides clomazone or triallate. A quantity of 15 kg phorate ha Weedy rice is one of the most damaging global weeds and a major threat to DSR systems. In this study we have developed a proof-of-concept method to allow selective weedy rice control in rice crops. We call for herbicide discovery programmes and research to identify candidate safener and herbicide combinations to achieve selective herbicide control of weedy rice and alleviate weed infestations in global rice crops. © 2016 Society of Chemical Industry.
Herbicide resistance in Bromus and Hordeum spp. in the Western Australian grain belt
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CP14293
Abstract: Random surveys conducted in the Western Australian (WA) grain belt have shown that herbicide-resistant Lolium rigidum and Raphanus raphanistrum are a widespread problem across the cropping region. In 2010, a random survey was conducted to establish the levels of herbicide resistance for common weed species in crop fields, including the minor but emerging weeds Bromus and Hordeum spp. This is the first random survey in WA to establish the frequency of herbicide resistance in these species. For the annual grass weed Bromus, 91 populations were collected, indicating that this species was present in % of fields. Nearly all populations were susceptible to the commonly used herbicides tested in this study however, a small number of populations (13%) displayed resistance to the acetolactate synthase-inhibiting sulfonylurea herbicides. Only one population displayed resistance to the acetyl-coenzyme A carboxylase-inhibiting herbicides. Forty-seven Hordeum populations were collected from 10% of fields, with most populations being susceptible to all herbicides tested. Of the Hordeum populations, 8% were resistant to the sulfonylurea herbicide sulfosulfuron, some with cross-resistance to the imidazolinone herbicides. No resistance was found to glyphosate or paraquat, although resistance to these herbicides has been documented elsewhere in Australia for Hordeum spp. (Victoria) and Bromus spp. (Victoria, South Australia and WA).
Characterisation of glufosinate resistance mechanisms in Eleusine indica
Publisher: Wiley
Date: 20-02-2017
DOI: 10.1002/PS.4528
Abstract: An Eleusine indica population has evolved resistance to glufosinate, a major post-emergence herbicide of global agriculture. This population was analysed for target-site (glutamine synthetase) and non-target-site (glufosinate uptake, translocation and metabolism) resistance mechanisms. Glutamine synthetase (GS) activity extracted from susceptible (S) and resistant (R*) plants was equally sensitive to glufosinate inhibition, with IC Glufosinate resistance in this resistant population is not due to an insensitive GS, or increased activity, or altered glufosinate uptake and translocation, or enhanced glufosinate metabolism. Thus, target-site resistance is likely excluded and the exact resistance mechanism(s) remain to be determined. © 2017 Society of Chemical Industry.
Demography of Salsola australis populations in the agricultural region of south‐west Australia
Publisher: Wiley
Date: 06-07-2009
Pollen-Mediated Movement of Herbicide Resistance Between Commercial Canola Fields
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-06-2002
Abstract: There is considerable public and scientific debate for and against genetically modified (GM) crops. One of the first GM crops, Brassica napus (oilseed rape or canola) is now widely grown in North America, with proposed commercial release into Australia and Europe. Among concerns of opponents to these crops are claims that pollen movement will cause unacceptable levels of gene flow from GM to non-GM crops or to related weedy species, resulting in genetic pollution of the environment. Therefore, quantifying pollen-mediated gene flow is vital for assessing the environmental impact of GM crops. This study quantifies at a landscape level the gene flow that occurs from herbicide-resistant canola crops to nearby crops not containing herbicide resistance genes.
A Survey in the Southern Grain Belt of Western Australia Did Not Find Conyza Spp. Resistant to Glyphosate
Publisher: Cambridge University Press (CUP)
Date: 09-2009
DOI: 10.1614/WT-08-166.1
Abstract: Glyphosate-resistant crops will be grown for the first time in Western Australia in 2009. A survey was conducted across 150,000 km 2 of the southeastern part of the Western Australian grain belt in 2007 to determine whether glyphosate-resistant Conyza populations were present. Sixty-eight Conyza populations were collected from various fields and roadside locations. These populations were collected from areas where Conyza was known to exist. Populations were screened with glyphosate and all populations were found to be glyphosate-susceptible. While no glyphosate-resistant Conyza populations were found in the southeastern grain belt of Western Australia, it provides baseline data prior to the introduction of glyphosate-resistant crops in this region. It is important to monitor the efficacy of glyphosate as resistance becomes more prevalent in weeds of various cropping systems worldwide.
The Potential for Pyroxasulfone to Selectively Control Resistant and Susceptible Rigid Ryegrass (Lolium rigidum) Biotypes in Australian Grain Crop Production Systems
Publisher: Cambridge University Press (CUP)
Date: 03-2011
Abstract: The widespread evolution of resistance in rigid ryegrass populations to the highly effective, in-crop, selective herbicides used within southern Australian grain-crop production systems has severely diminished the available herbicide resource. A new PRE grass-selective herbicide, pyroxasulfone, may offer Australian grain producers a new option for rigid ryegrass control in wheat crops. The efficacy and level of selectivity of rigid ryegrass control with pyroxasulfone was investigated for a range of annual crop species in potted-plant, dose–response studies. In comparison with other currently available PRE herbicides, pyroxasulfone provided effective control of both resistant and susceptible rigid ryegrass populations. Additionally, control of these populations was achieved at rates that had little or no effect on the growth and survival of wheat. This crop was also the most tolerant of cereal species, with triticale, barley, and oat being more injured at higher pyroxasulfone rates than wheat was. In general though, pulse-crop species were found to be more tolerant of high pyroxasulfone rates than cereal-crop species. There were subtle effects of soil type on the efficacy of pyroxasulfone, where higher rates were required to achieve effective control on soils with higher clay or organic matter contents. The ability of pyroxasulfone to selectively control resistant and susceptible rigid ryegrass populations as identified in these studies clearly indicate the potential for widespread use and success of this herbicide in Australian cropping systems.
Six amino acid substitutions in the carboxyl‐transferase domain of the plastidic acetyl‐CoA carboxylase gene are linked with resistance to herbicides in a Lolium rigidum population
Publisher: Wiley
Date: 11-09-2006
DOI: 10.1111/J.1469-8137.2006.01879.X
Abstract: The molecular basis of an acetyl-CoA carboxylase (ACCase) target-based resistant Lolium rigidum population (WLR 96) was studied here. The carboxyl-transferase domain of the plastidic ACCase gene from resistant in iduals was lified by PCR and sequenced. The DNA sequences were aligned and compared with a susceptible population. Six amino acid substitutions were identified in the resistant population. The substitution Ile-2041-Asn, known to confer resistance to ACCase-inhibiting herbicides aryloxyphenoxypropionate (APP) in Alopecurus myosuroides, was identified in most resistant plants but it is always linked with other amino acid substitutions. This was confirmed by a cleaved lified polymorphism (CAP) marker and an allele-specific PCR. The sole amino acid substitution Ile-2041-Asn was not found in this population. It is likely this mutation evolved later among in iduals already possessing the other substitutions. Three haplotypes were identified from the resistant population based on the six amino acid combinations, and two are linked with herbicide resistance in this population. The multiple amino acid substitutions including the Ile-2041-Asn form the molecular basis endowing a high degree of resistance to ACCase-inhibiting herbicides in this L. rigidum population.
An Herbicide-Susceptible Rigid Ryegrass (Lolium rigidum) Population Made Even More Susceptible
Publisher: Cambridge University Press (CUP)
Date: 03-2012
Abstract: A wild population of a plant species, especially a cross-pollinated species, can display considerable genetic variation. Genetic variability is evident in differential susceptibility to an herbicide because the population can show continuous phenotypic variation. Recent, recurrent selection studies have revealed that phenotypic variation in response to low herbicide rates is heritable and can result in rapid evolution of herbicide resistance in genetically variable cross-pollinated rigid ryegrass. In this study, the heritable genetic variation in an herbicide-susceptible rigid ryegrass population was exploited to shift the population toward greater herbicide susceptibility by recurrent selection. To enhance herbicide susceptibility, herbicide-susceptible rigid ryegrass plants were ided into two identical clones, and one series of cloned plants was treated with a low rate of herbicide (diclofop). The nontreated clones of in iduals that did not survive the herbicide treatment were selected and bulk-crossed to obtain the susceptible progeny. After two cycles of selection, the overall susceptibility to diclofop was doubled. The results indicate that minor genes for resistance are present in an herbicide-susceptible rigid ryegrass population, and their exclusion can increase susceptibility to diclofop.
MALATHION ANTAGONIZES METABOLISM-BASED CHLORSULFURON RESISTANCE IN LOLIUM-RIGIDUM
Publisher: Elsevier BV
Date: 07-1994
Evolution of glyphosate resistance in a Lolium rigidum population by glyphosate selection at sublethal doses
Publisher: Springer Science and Business Media LLC
Date: 03-06-2009
DOI: 10.1038/HDY.2009.64
Abstract: The majority of the documented cases of field-evolved herbicide-resistant weed biotypes established that single major genes confer glyphosate resistance. However, the contribution of minor genes endowing substantial plant survival at sublethal herbicide doses may be a potential complementary path to herbicide resistance evolution in weed populations under selection. Here, we subjected a number of susceptible in iduals of Lolium rigidum to recurrent glyphosate selection to test the potential for sublethal glyphosate doses to additively select for glyphosate resistance. After 3-4 cycles of glyphosate selection in two distinct environments, the progenies of the initially susceptible population were shifted toward glyphosate resistance. The results indicate progressive enrichment of minor gene trait(s) contributing toward plant survival in the glyphosate-selected progenies. After three generations of selection, the estimated LD(50) values were doubled compared with the original population and up to 33% plant survival was obtained in the glyphosate-selected progeny at the recommended glyphosate label rate. This level of resistance probably was the maximum shift achievable with sublethal glyphosate dose selection in this small population. Cross-pollination was a crucial factor enabling the rapid rate of accumulation of minor glyphosate resistance gene trait(s) that are likely to be present at a relatively high frequency in a small susceptible population. The mechanistic basis of the moderate glyphosate resistance level selected by sublethal glyphosate doses remains unknown and warrants future research. Studying the main factors influencing the evolution of resistant weed populations is crucial for understanding, predicting and managing herbicide resistance.
ALS gene proline (197) mutations confer ALS herbicide resistance in eight separated wild radish (Raphanus raphanistrum) populations
Publisher: Cambridge University Press (CUP)
Date: 12-2003
DOI: 10.1614/02-166
Abstract: The biochemical and molecular basis of resistance to acetolactate synthase (ALS)–inhibiting herbicides was investigated in eight resistant (R) and three susceptible (S) wild radish populations. In vitro enzyme assays revealed an ALS herbicide–resistant ALS enzyme in all R populations. ALS enzyme extracted from the shoots of all eight R populations was highly resistant to the ALS-inhibiting sulfonylurea herbicide chlorsulfuron (20- to 160-fold) and the triazolopyrimidine herbicide metosulam (10- to 46-fold) and moderately resistant to metsulfuron (three to eightfold). There was little or no cross-resistance to the imidazolinone herbicides imazapyr and imazethapyr. The ALS gene fragment covering potential mutation sites in these populations was lified, sequenced, and compared. All eight R populations had point mutations in the codon for the proline residue in Domain A. However, the point mutations varied and encoded four different amino acid substitutions: histidine, threonine, alanine, and serine. No nucleotide difference in the DNA sequence of Domains C and D resulting in amino acid substitutions was observed between the R and S populations examined. In addition, a three- to fivefold higher ALS-specific activity was consistently observed in all R populations compared with S populations, whereas Northern blot analysis detected a similar level of ALS mRNA, suggesting a possible translational–posttranslational regulation of the enzyme. It is concluded that selection pressure from chlorsulfuron on eight separate wild radish populations has resulted in target site mutation at the same proline residue in the ALS gene. Higher ALS activity also may play a role in the resistance level.
Herbicide-Resistant Weed Seeds Contaminate Grain Sown in the Western Australian Grainbelt
Publisher: Cambridge University Press (CUP)
Date: 12-2010
Abstract: Preventing the introduction of weeds into the farming system through sowing of clean seeds is an essential component of weed management. The weed seed contamination of cleaned grain and herbicide resistance levels of the recovered weed seeds were examined in a study conducted across 74 farms in the Western Australian grainbelt. Most farmers grew and conserved their own crop seed. The majority of cleaned s les had some level of seed contamination from 11 foreign weed and volunteer crop species, with an average of 62 seeds 10 kg −1 grain, substantially higher than the 28 seeds 10 kg −1 grain expected by farmers. The most common weed contaminants across all s les were rigid ryegrass, wild radish, brome, and wild oat. When categorized by crop type, rigid ryegrass was the most frequent contaminant of cereal crops (barley and wheat), however wild radish was the most frequent contaminant of lupin crops. Uncleaned crop seed s les had almost 25 times more contamination than cleaned crop seed. Herbicide resistance was highly prevalent within rigid ryegrass populations recovered from cleaned grain except for glyphosate, which controlled all populations tested. Some resistance was also found in wild radish and wild oat populations however, brome was susceptible to fluazifop. This study has shown that farmers are unknowingly introducing weed seeds into their farming systems during crop seeding, many of which have herbicide resistance.
Reduced efficacy and enhanced degradation of carbetamide after repeated application in Australia
Publisher: Wiley
Date: 06-1997
Selective Inhibition of a Cytochrome P450 Enzyme in Wheat That Oxidizes Both the Natural Substrate Lauric Acid and the Synthetic Herbicide Diclofop
Publisher: Elsevier BV
Date: 03-1996
Enhanced herbicide metabolism induced by 2,4‐D in herbicide susceptible Lolium rigidum provides protection against diclofop‐methyl
Publisher: Wiley
Date: 20-06-2013
DOI: 10.1002/PS.3552
Abstract: The auxinic herbicide 2,4-D amine is known, in vitro, as a cytochrome P450 inducer. The current study uses 2,4-D pre-treatment, at the whole plant level, to study mechanism(s) of non-target site based herbicide resistance to the ACCase-inhibiting herbicide diclofop-methyl in Lolium rigidum. The 2,4-D pre-treatment caused up to 10-fold shift in LD50 and GR50 in dose-response to subsequently applied diclofop-methyl in a herbicide susceptible L. rigidum population. Foliar uptake and translocation of (14) C-diclofop-methyl did not differ in 2,4-D pre-treated versus untreated plants. HPLC analysis revealed that de-esterification of diclofop-methyl to toxic diclofop acid was similar, but further metabolism of diclofop acid to non-toxic metabolites was significantly (1.8-fold) faster in 2,4-D pre-treated than untreated plants. HPLC profile of major polar metabolites was similar when L. rigidum and diclofop-methyl tolerant wheat were compared, but wheat metabolised diclofop acid three-fold faster than L. rigidum. In addition, 2,4-D pre-treatment also induced cross-protection against the ALS-inhibiting herbicide chlorsulfuron, and the known P450 inhibitor malathion can reverse this effect. Protection against diclofop-methyl provided by 2,4-D pre-treatment in susceptible L. rigidum is associated with higher rates of herbicide metabolism, mirroring that identified in field-evolved, non-target site-based diclofop-methyl resistant populations. 2,4-D may induce higher level expression of herbicide-metabolising genes hence providing protection, and therefore, this 2,4-D induction system can be used, in combination with other genomic approaches, to assist isolating cytochrome P450 and other genes that are involved in herbicide metabolism and endow herbicide resistance in L. rigidum.
Non‐target‐site resistance to PDS‐inhibiting herbicides in a wild radish (Raphanus raphanistrum ) population
Publisher: Wiley
Date: 10-01-2020
DOI: 10.1002/PS.5733
Abstract: Diflufenican resistance has been reported in wild radish populations since 1998, but the resistance mechanisms have not been investigated. Recently, we identified a wild radish population (H2/10) from the Western Australian grain belt that is resistant (R) to the phytoene desaturase (PDS)-inhibiting herbicide diflufenican. Dose-response results showed this R population is 4.9-fold more resistant than the susceptible (S) population based on the LD These results demonstrated that diflufenican resistance in this R wild radish population is likely due to non-target-site based enhanced herbicide metabolism involving cytochrome P450s. © 2019 Society of Chemical Industry.
Identification of glyphosate-resistant Lolium rigidum and Raphanus raphanistrum populations within the first Western Australian plantings of transgenic glyphosate-resistant canola
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CP15031
Abstract: Transgenic glyphosate-resistant canola was first commercially grown in Western Australia (WA) in 2010, providing an opportunity to obtain important baseline data regarding the level of glyphosate resistance in weeds following the exclusive use of glyphosate for in-crop weed control. In this study, two surveys (2010 and 2011) were conducted across the 14 Mha of the grainbelt of WA. The 2010 survey was carried out at the late-flowering stage of glyphosate-resistant canola, whereas the 2011 survey was conducted at an earlier growth stage (6–8 leaves), ~2–3 weeks after the second in-crop glyphosate application. During the surveys, 239 fields were visited, representing an estimated combined area of 24 000 ha. The 2011 survey alone represented a subs le of 23% of the total glyphosate-resistant canola planting in the WA grainbelt for that season. Glyphosate resistance was identified in one population of wild radish (Raphanus raphanistrum L.) and in eight annual ryegrass (Lolium rigidum L.) populations. None of the tested capeweed (Arctotheca calendula (L.) Levyns) populations were glyphosate-resistant. In this survey, no populations of barley grass (Hordeum spp.), brome grass (Bromus spp.), wild oat (Avena spp.) or small-flowered mallow (Malva parviflora L.) survived glyphosate application. Despite a long history of pre-seeding and fallow glyphosate use in WA, this survey found that glyphosate still provides excellent in-crop control of most species however, some resistance is evident, requiring erse weed control techniques to limit their spread.
Do plants pay a fitness cost to be resistant to glyphosate?
Publisher: Wiley
Date: 13-03-2019
DOI: 10.1111/NPH.15733
Abstract: We reviewed the literature to understand the effects of glyphosate resistance on plant fitness at the molecular, biochemical and physiological levels. A number of correlations between enzyme characteristics and glyphosate resistance imply the existence of a plant fitness cost associated with resistance-conferring mutations in the glyphosate target enzyme, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). These biochemical changes result in a tradeoff between the glyphosate resistance of the EPSPS enzyme and its catalytic activity. Mutations that endow the highest resistance are more likely to decrease catalytic activity by reducing the affinity of EPSPS for its natural substrate, and/or slowing the velocity of the enzyme reaction, and are thus very likely to endow a substantial plant fitness cost. Prediction of fitness costs associated with EPSPS gene lification and overexpression can be more problematic. The validity of cost prediction based on the theory of evolution of gene expression and resource allocation has been cast into doubt by contradictory experimental evidence. Further research providing insights into the role of the EPSPS cassette in weed adaptation, and estimations of the energy budget involved in EPSPS lification and overexpression are required to understand and predict the biochemical and physiological bases of the fitness cost of glyphosate resistance.
Dinitroaniline Herbicide Resistance and Mechanisms in Weeds
Publisher: Frontiers Media SA
Date: 25-03-2021
Abstract: Dinitroanilines are microtubule inhibitors, targeting tubulin proteins in plants and protists. Dinitroaniline herbicides, such as trifluralin, pendimethalin and oryzalin, have been used as pre-emergence herbicides for weed control for decades. With widespread resistance to post-emergence herbicides in weeds, the use of pre-emergence herbicides such as dinitroanilines has increased, in part, due to relatively slow evolution of resistance in weeds to these herbicides. Target-site resistance (TSR) to dinitroaniline herbicides due to point mutations in α-tubulin genes has been confirmed in a few weedy plant species (e.g., Eleusine indica , Setaria viridis , and recently in Lolium rigidum ). Of particular interest is the resistance mutation Arg-243-Met identified from dinitroaniline-resistant L. rigidum that causes helical growth when plants are homozygous for the mutation. The recessive nature of the TSR, plus possible fitness cost for some resistance mutations, likely slows resistance evolution. Furthermore, non-target-site resistance (NTSR) to dinitroanilines has been rarely reported and only confirmed in Lolium rigidum due to enhanced herbicide metabolism (metabolic resistance). A cytochrome P450 gene (CYP81A10) has been recently identified in L. rigidum that confers resistance to trifluralin. Moreover, TSR and NTSR have been shown to co-exist in the same weedy species, population, and plant. The implication of knowledge and information on TSR and NTSR in management of dinitroaniline resistance is discussed.
Inhibition of photosynthetic reactions under water stress: interaction with light level
Publisher: Springer Science and Business Media LLC
Date: 1984
DOI: 10.1007/BF00407081
Multiple resistance to dissimilar herbicide chemistries in a biotype of Lolium rigidum due to enhanced activity of several herbicide degrading enzymes
Publisher: Elsevier BV
Date: 02-1996
Metribuzin resistance via enhanced metabolism in a multiple herbicide resistant Lolium rigidum population
Publisher: Wiley
Date: 17-06-2020
DOI: 10.1002/PS.5929
Transgenic glyphosate-resistant canola (Brassica napus) can persist outside agricultural fields in Australia
Publisher: Elsevier BV
Date: 03-2016
Herbicide discovery through innovation and diversity
Publisher: Advances in Weed Science
Date: 2022
Direct measurement of paraquat in leaf protoplasts indicates vacuolar paraquat sequestration as a resistance mechanism in Lolium rigidum
Publisher: Elsevier BV
Date: 09-2010
High Frequency of Chlorsulfuron-Resistant Wild Radish (Raphanus raphanistrum) Populations across the Western Australian Wheatbelt1
Publisher: Cambridge University Press (CUP)
Date: 04-2001
Effect of herbicide resistance endowing Ile-1781-Leu and Asp-2078-GlyACCasegene mutations on ACCase kinetics and growth traits inLolium rigidum
Publisher: Oxford University Press (OUP)
Date: 26-05-2015
DOI: 10.1093/JXB/ERV248
Influence of crop competition and harvest weed seed control on Rigid Ryegrass (Lolium rigidum) seed retention height in wheat crop canopies
Publisher: Cambridge University Press (CUP)
Date: 17-07-2018
DOI: 10.1017/WSC.2018.28
Abstract: Harvest weed seed control (HWSC) is an Australian innovation, developed to target high proportions of weed seed retained at crop maturity by many major weed species. There is the potential, however, that a reduction in the average height of retained seed is an adaptation to the long-term use of HWSC practices. With the aim of examining the distribution of rigid ryegrass ( Lolium rigidum Gaudin) seed through crop canopies, a survey of Australian wheat ( Triticum aestivum L.) fields was conducted at crop maturity. Nine sites with medium to long-term HWSC use were specifically included to examine the influence of HWSC use on seed retention height. During the 2013 wheat harvest, L. rigidum and wheat plant s les were collected at five heights downward through the crop canopy (40, 30, 20, 10, and 0 cm above ground level) in 71 wheat fields. Increased crop competition resulted in higher proportions of L. rigidum seed in the upper crop canopy ( cm). The increase in plant height is likely a shade-intolerance response of L. rigidum plants attempting to capture more light. This plant attribute creates the opportunity to use crop competition to improve HWSC efficacy by increasing the average height of seed retention. Crop competition can, therefore, have a double impact by reducing overall L. rigidum seed production and increasing seed retention height. Examining the distribution of wheat biomass and L. rigidum seed through the crop canopy, we determined that reducing harvest height for HWSC considerably increased the collection of L. rigidum seed (25%) but to a lesser extent wheat crop biomass (14%). Comparison of + and − HWSC use at nine locations found no evidence of adaptation to this form of weed control following 5 to 10 yr of use. Although the potential for resistance to HWSC remains, these results indicate that this will not readily occur in the field.
How do spatial heterogeneity and dispersal in weed population models affect predictions of herbicide resistance evolution?
Publisher: Elsevier BV
Date: 10-2017
Response to low-dose herbicide selection in self-pollinatedAvena fatua
Publisher: Wiley
Date: 22-05-2015
DOI: 10.1002/PS.4032
Abstract: When applied at the correct plant stage and dose, herbicides are highly toxic to plants. At reduced, low herbicide doses (below the recommended dose) plants can survive and display continuous and quantitative variation in dose-survival responses. Recurrent (directional) selection studies can reveal whether such a phenotypic variation in plant survival response to low herbicide dose is heritable and leads to herbicide resistance. In a common experimental garden study, we have subjected a susceptible population of self-pollinated hexaploid Avena fatua to low-dose recurrent selection with the ACCase-inhibiting herbicide diclofop-methyl for three consecutive generations. Significant differences in response to low-dose diclofop-methyl selection were observed between the selected progenies and parent plants, with a twofold diclofop-methyl resistance and cross-resistance to ALS-inhibiting herbicides. Thus, the capacity of self-pollinated A. fatua to respond to low-dose herbicide selection is marginal, and it is much lower than in cross-pollinated L. rigidum. Lolium rigidum in the same experiment evolved 40-fold diclofop-methyl resistance by progressive enrichment of quantitative resistance-endowing traits. Cross-pollination rate, genetic variation and ploidy levels are identified as possible drivers affecting the contrasting capacity of Avena versus Lolium plants to respond to herbicide selection and the subsequent likelihood of resistance evolution at low herbicide dose usage.
Evolution of herbicide resistance in weeds: initial frequency of target site-based resistance to acetolactate synthase-inhibiting herbicides in Lolium rigidum
Publisher: Springer Science and Business Media LLC
Date: 2002
Abstract: The frequency of in iduals resistant to two acetolactate synthase (ALS)-inhibiting herbicides in three previously untreated populations of Lolium rigidum was determined. The frequency of in iduals resistant to the sulfonylurea herbicide sulfometuron-methyl varied from 2.2 x 10(-5) to 1.2 x 10(-4) and the frequency of in iduals resistant to the imidazolinone herbicide imazapyr varied from 1 x 10(-5) to 5.8 x 10(-5) depending on the population. Application of sulfometuron-methyl selected in iduals with a herbicide-insensitive ALS, which was also cross-resistant to imazapyr. The high initial frequency of in iduals resistant to ALS-inhibiting herbicides in L. rigidumpopulations never previously exposed to these herbicides helps explain the rapid evolution of herbicide resistance in this species once ALS-inhibiting herbicides were used.
Glyphosate‐Resistant Weeds and Crops
Publisher: Wiley
Date: 13-03-2008
DOI: 10.1002/PS.1561
Target-site EPSPS Pro-106 mutations: sufficient to endow glyphosate resistance in polyploidEchinochloa colona?
Publisher: Wiley
Date: 06-2015
DOI: 10.1002/PS.4038
Abstract: This study confirms and characterises glyphosate resistance in two polyploid Echinochloa colona populations from north-eastern Australia. Glyphosate dose response revealed that the two resistant populations were marginally (up to twofold) resistant to glyphosate. Resistant plants did not differ in non-target-site foliar uptake and translocation of (14) C-glyphosate, but contained the known target-site 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) mutation Pro-106-Thr and/or Pro-106-Leu. Although plants carrying either a single or two EPSPS mutations were glyphosate resistant relative to the susceptible population, they were still controlled at the field rate of glyphosate (450 g a.e. ha(-1) ) when treated under warm conditions (25/20 °C). However, when treated in hot conditions (35/30 °C), most mutant resistant plants (68%) can survive the field rate, and an increase (2.5-fold) in glyphosate LD50 was found for both the R and S populations. This study shows that one or two EPSPS Pro-106 mutations are insufficient to confer field-rate glyphosate resistance in polyploidy E. colona at mild temperatures. However, control of these mutant plants at the glyphosate field rate is poor at high temperatures, probably owing to reduced glyphosate efficacy. Therefore, glyphosate should be applied during relatively mild (warm) temperature periods in the summer growing season to improve E. colona control.
Non-target-site glyphosate resistance in Echinochloa colona from Western Australia
Publisher: Elsevier BV
Date: 10-2018
Modeling the Impact of Harvest Weed Seed Control on Herbicide-Resistance Evolution
Publisher: Cambridge University Press (CUP)
Date: 05-2018
DOI: 10.1017/WSC.2018.9
Abstract: Harvest weed seed control (HWSC) techniques have been implemented in Australian cropping systems to target and reduce the number of weed seeds entering the seedbank and thereby reduce the number of problematic weeds emerging in subsequent years to infest subsequent crops. However, the influence of HWSC on ameliorating herbicide-resistance (HR) evolution has not been investigated. This research used integrated spatial modeling to examine how the frequency and efficacy of HWSC affected the evolution of resistance to initially effective herbicides. Herbicides were, in all cases, better protected from future resistance evolution when their use was combined with annual HWSC. Outbreaks of multiple HR were very unlikely to occur and were nearly always eliminated by adding annual, efficient HWSC. The efficacy of the HWSC was important, with greater reductions in the number of resistance genes achieved with higher-efficacy HWSC. Annual HWSC was necessary to protect sequences of lower-efficacy herbicides, but HWSC could still protect herbicides if it was used less often than once per year, when the HWSC and the herbicides were highly effective. Our results highlight the potential benefits of combining HWSC with effective herbicides for controlling weed populations and reducing the future evolution of HR.
Assessment of management options for Salsola australis in south‐west Australia by transition matrix modelling
Publisher: Wiley
Date: 06-07-2009
Evolved Glyphosate Resistance in Plants: Biochemical and Genetic Basis of Resistance
Publisher: Cambridge University Press (CUP)
Date: 06-2006
DOI: 10.1614/WT-04-142R.1
Abstract: Resistance to the herbicide glyphosate is currently known in at least eight weed species from many countries. Some populations of goosegrass from Malaysia, rigid ryegrass from Australia, and Italian ryegrass from Chile exhibit target site–based resistance to glyphosate through changes at amino acid 106 of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene. Mutations change amino acid 106 from proline to either serine or threonine, conferring an EPSPS weakly resistant to glyphosate. The moderate level of resistance is sufficient for commercial failure of the herbicide to control these plants in the field. Conversely, a nontarget site resistance mechanism has been documented in glyphosate-resistant populations of horseweed and rigid ryegrass from the United States and Australia, respectively. In these resistant plants, there is reduced translocation of glyphosate to meristematic tissues. Both of these mechanisms are inherited as a single, nuclear gene trait. Although at present only two glyphosate-resistance mechanisms are known, it is likely that other mechanisms will become evident. The already very large and still increasing reliance on glyphosate in many parts of the world will inevitably result in more glyphosate-resistant weeds, placing the sustainability of this precious herbicide resource at risk.
Mechanism of Paraquat Resistance in Hordeum glaucum. I. Studies With Isolated Organelles and Enzymes
Publisher: CSIRO Publishing
Date: 1987
DOI: 10.1071/PP9870081
Abstract: The mechanism of resistance to paraquat was studied in a biotype of the important and widespread weed, Hordeum glaucum Steud. (barley grass). Experiments with isolated chloroplasts and protoplasts from resistant and susceptible plants established that resistance is not due to any change in the active site of paraquat binding. No difference was found in the permeability of paraquat through the plasmalemma or chloroplast envelope membranes. As paraquat catalyses the production of excited oxygen states, the capacity of varying enzymic means of detoxifying these destructive species was examined. No differences between leaf tissue of resistant and susceptible plants were found in the activities of superoxide dismutase, catalase or peroxidases. These experiments establish that, if paraquat enters the symplast of the resistant biotype, it will exert its herbicidal effect in the normal way. Thus the resistant plants must have the ability to prevent paraquat from entering the symplast.
Chlamydomonas reinhardtii as a model system for pro-active herbicide resistance evolution research
Publisher: Oxford University Press (OUP)
Date: 23-05-2007
Selection for low dormancy in annual ryegrass (Lolium rigidum) seeds results in high constitutive expression of a glucose-responsive α-amylase isoform
Publisher: Oxford University Press (OUP)
Date: 21-09-2012
DOI: 10.1093/AOB/MCS213
Green and blue light photoreceptors are involved in maintenance of dormancy in imbibed annual ryegrass (Lolium rigidum) seeds
Publisher: Wiley
Date: 02-09-2008
DOI: 10.1111/J.1469-8137.2008.02570.X
Abstract: Light plays an important role in two separate processes within the seeds of Lolium rigidum (annual ryegrass). Dormant seeds of L. rigidum remain dormant when imbibed in the light, but once seeds have lost dormancy through dark-stratification, light stimulates their germination. This study characterizes the light qualities and quantities which are effective in maintenance of dormancy. Dormant seeds were stratified under narrow- and broad-waveband light to identify the potential photoreceptors involved in dormancy maintenance, and to determine whether dark-induced dormancy loss is reversible by light. Blue and green light both mediated dormancy maintenance in a far-red-independent manner. Red light resulted in dormancy maintenance only when far-red wavelengths were excluded, suggesting a redundant function of phytochrome. At low fluence rates, white light was more effective than monochromatic light, suggesting the action of multiple photoreceptors in dormancy maintenance. By contrast, nondormant seeds did not germinate unless provided with red light. These results indicate that seed dormancy maintenance is potentially mediated through the actions of blue and green light photoreceptors. Seed dormancy could thus be added to the growing list of plant responses that may be mediated by green light in a cryptochrome-independent manner.
Challenging glyphosate resistance EPSPS P106S and TIPS mutations with soybean competition and glyphosate: implications for management
Publisher: Wiley
Date: 18-08-2022
DOI: 10.1002/PS.7096
Abstract: Eleusine indica (L.) Gaertn. (goosegrass) is a major weed in global cropping systems. It has evolved resistance to glyphosate due to single Pro‐106‐Ser (P106S) or double Thr‐102‐Ile + Pro‐106‐Ser (TIPS) EPSPS target site mutations. Here, experiments were conducted to evaluate the single effect of soybean competition and its combined effect with a glyphosate field dose (1080 g ae ha −1 ) on the growth and fitness of plants carrying these glyphosate resistance endowing target site mutations. TIPS E. indica plants are highly glyphosate‐resistant but the double mutation endows a substantial fitness cost. The TIPS fitness penalty increased under the effect of soybean competition resulting in a cost of 95%, 95% and 96% in terms of, respectively, vegetative growth, seed mass and seed number investment. Glyphosate treatment of these glyphosate‐resistant TIPS plants showed an increase in growth relative to those without glyphosate. Conversely, for the P106S moderate glyphosate resistance mutation, glyphosate treatment alone reduced survival rate, vegetative growth, aboveground biomass (34%), seed mass (48%) and number (52%) of P106S plants relative to the glyphosate nontreated plants. However, under the combined effects of both soybean competition and the field‐recommended glyphosate dose, vegetative growth, aboveground biomass, seed mass and number of P106S and TIPS plants were substantially limited (by ≤99%). The ecological environment imposed by intense competition from a soybean crop sets a significant constraint for the landscape‐level increase of both the E. indica single and double glyphosate resistance mutations in the agroecosystem and highlights the key role of crop competition in limiting the population growth of weeds, whether they are herbicide‐resistant or susceptible. © 2022 Society of Chemical Industry.
Investigations of mechanisms of resistance to bipyridyl herbicides in Arctotheca calendula (L.) Levyns
Publisher: Wiley
Date: 10-1994
Does cutting herbicide rates threaten the sustainability of weed management in cropping systems?
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.JTBI.2011.05.010
Abstract: Evolution of herbicide resistance in weeds is a growing problem across the world, and it has been suggested that low herbicide rates may be contributing to this problem. An in idual-based simulation model that represents weed population dynamics and the evolution of polygenic herbicide resistance was constructed and used to investigate whether using lower herbicide rates or standard rates at reduced efficacy could reduce the sustainability of cropping systems by causing faster increases in weed population density as herbicide resistance develops. A number of different possible genetic bases for resistance were considered, including monogenic resistance and polygenic resistance conferred by several genes. The results show that cutting herbicide rates does not affect the rate at which weed densities reach critical levels when resistance is conferred exclusively by a single dominant gene. In some polygenic situations, cutting herbicide rates substantially reduces sustainability, due to a combination of faster increase in resistance gene frequency and reduced kill rates in all genotypes, while in other polygenic situations the effect is small. Differences in sustainability depend on combined strength of the resistance genes, variability in phenotypic susceptibility and rate delivered, level of control due to alternative measures, and degree of genetic dominance and epistasis. In the situation where resistance can be conferred by both a single dominant major gene or a number of co-dominant minor genes in combination, the difference made by low rates depends on the relative initial frequency of the major and minor genes. These results show that careful consideration of herbicide rate and understanding the genetic basis of resistance are important aspects of weed management.
Polyamines can inhibit paraquat toxicity and translocation in the broadleaf weed Arctotheca calendula
Publisher: Elsevier BV
Date: 10-2004
Long distance pollen-mediated flow of herbicide resistance genes in Lolium rigidum
Publisher: Springer Science and Business Media LLC
Date: 02-09-2008
DOI: 10.1007/S00122-008-0862-8
Abstract: Gene flow promotes genetic exchange among plant populations mediating evolutionary dynamics yet, the importance of gene flow at distance via pollen movement is poorly understood. A field experiment at the landscape level was conducted with Lolium rigidum herbicide-susceptible in iduals (population VLR1) placed into an otherwise Lolium-free bushland environment at increasing distances from adjacent large commercial crop fields infested with herbicide-resistant L. rigidum. Herbicide resistance was used as a marker to quantify the distance and the rate of pollen-mediated gene flow. About 21,245 seeds were produced on the isolated, susceptible mother plants of which 3,303 seedlings were tested for herbicide resistance and 664 seedlings were found to be resistant. Pollen-mediated gene flow occurred at 3,000 m (maximum tested distance). Both Mendelian and molecular analyses (sequencing and CAPS markers) confirmed the introgression of herbicide resistance genes. This is the first documented case of long-distance gene flow in L. rigidum. The results are important for future modeling simulations of herbicide resistance evolution and subsequent mobility. The adoption of integrated agronomic strategies, the control of potential receptor plants on fields' margins and conservative use of herbicides can be realistic options to minimize herbicide resistance spread.
Simulating evolution of glyphosate resistance in Lolium rigidum II: past, present and future glyphosate use in Australian cropping
Publisher: Wiley
Date: 18-11-2003
Inheritance of evolved glyphosate resistance in Lolium rigidum (Gaud.)
Publisher: Springer Science and Business Media LLC
Date: 03-2001
Light-dependent enhanced metabolism of chlorotoluron in a substituted urea herbicide-resistant biotype ofLolium rigidum Gaud.
Publisher: Springer Science and Business Media LLC
Date: 1997
DOI: 10.1007/BF01007705
Quinclorac Resistance in Echinochloa crus-galli from China
Publisher: Elsevier BV
Date: 09-2019
Increased Detoxification Is a Mechanism of Simazine Resistance in Lolium rigidum
Publisher: Elsevier BV
Date: 07-1993
Integrating Herbicide Programs with Harvest Weed Seed Control and Other Fall Management Practices for the Control of Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri)
Publisher: Cambridge University Press (CUP)
Date: 09-2016
Abstract: A large-plot field experiment was conducted at Keiser, AR, from fall of 2010 through fall of 2013 to understand to what extent soybean in-crop herbicide programs and postharvest fall management practices impact Palmer amaranth population density and seed production over three growing seasons. The effect of POST-only (glyphosate-only) or PRE followed by (fb) POST (glyphosate or glufosinate) + residual herbicide treatments were evaluated alone and in combination with postharvest management options of soybean residue spreading or soil incorporation, use of cover crops, windrowing with/without burning, and residue removal. Significant differences were observed between fall management practices on Palmer amaranth population density each fall. The use of cover crops and residue collection and removal fb the incorporation of crop residues into soil during the formation of beds were the most effective practices in reducing Palmer amaranth population. In contrast, the effects of fall management practices on Palmer amaranth seed production were inconsistent among years. The inclusion of a PRE herbicide application into the herbicide program significantly reduced Palmer amaranth population density and subsequent seed production each year when compared to the glyphosate-only program. Additionally, the glufosinate-containing residual program was superior to the glyphosate-containing residual program in reducing Palmer amaranth seed production. PRE fb POST herbicides resulted in significant decreases in the Palmer amaranth population density and seed production compared to POST application of glyphosate alone for all fall management practices, including the no-till practice. This study demonstrated that crop residue management such as chaff removal from the field, the use of cover crops, or seed incorporation during bed formation in combination with an effective PRE plus POST residual herbicide program is important for optimizing in-season management of Palmer amaranth and subsequently reducing the population density, which has a profound impact on lessening the risk for herbicide resistance and the consistency and effectiveness of future weed management efforts.
Herbicide multiple-resistance in a Lolium rigidum biotype is endowed by multiple mechanisms: isolation of a subset with resistant acetyl-CoA carboxylase
Publisher: Wiley
Date: 07-1994
Ecological fitness of a multiple herbicide-resistant Lolium rigidum population: dynamics of seed germination and seedling emergence of resistant and susceptible phenotypes
Publisher: Wiley
Date: 04-2005
Impact of crop-topping and swathing on the viable seed production of wild radish (Raphanus raphanistrum)
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/CP08286
Abstract: Crop-topping, the practice of applying non-selective herbicides at crop maturity, has proved to be an effective management technique in preventing the input of seed into the seedbank for some annual weed species of southern Australian crop production systems. However, the efficacy of this practice on the dominant broad-leaf weed of these systems, wild radish, is not well understood. These studies investigated the effect of crop-topping and swathing on the viable seed production of wild radish. Crop-topping with either glyphosate or sprayseed (paraquat 135 g/L + diquat 115 g/L) can provide large reductions of 80–90% in viable seed production of wild radish plants present in crops at the end of the growing season. However, the efficacy of this practice was found to be highly variable and therefore, cannot be relied upon to consistently produce these large reductions in seed numbers. Similarly, swathing also produced large reductions in viable seed production but results from this practice were even less consistent than crop-topping treatments. For all treatments, early application timings of growth stage 6.5 or earlier, were optimum for targeting wild radish seed production. However, these treatment timings also resulted in large crop yield losses of ~30%. To preserve at least 90% of crop yield, crop-topping and swathing treatments need to be delayed until wild radish growth stage 8.5, with expected reductions in seed numbers of up to 70%. However, in high-density infestations the need to preserve grain yield will be less important than preventing substantial inputs of wild radish seed into the seedbank.
Late-season non-selective herbicide application reduces Lolium rigidum seed numbers, seed viability, and seedling fitness
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/AR05122
Abstract: Experiments were conducted to investigate the effect of Lolium rigidum (annual ryegrass) seed developmental stage and application rate of glyphosate and SpraySeed (paraquat 135 g/L + diquat 115 g/L) on the number, germinability, and fitness of seeds produced. Glyphosate (450 g/L) was most effective when applied at a rate of 0.5–1 L/ha during heading and anthesis, reducing the number of filled seeds produced compared with unsprayed plants. Application post-anthesis, when seeds were at the milk to soft dough stage, was less effective. SpraySeed was most effective when applied post-anthesis, during the milk and early dough stages of seed development at a rate of 0.5–1 L/ha, resulting in the production of few viable seeds. Although some filled seeds were produced, most of the seeds were dead. Application during anthesis or once the seeds reached soft dough stage was less effective. For both herbicides, those seeds that were capable of germinating were smaller and had slower radicle and coleoptile growth, resulting in slower early seedling growth and reduced biomass production within the first month of growth. Additionally, glyphosate application reduced the proportion of seeds exhibiting dormancy. The anticipated reduction in seed competitive ability and altered emergence timing resulting from late-season herbicide application, even when application timing is not optimal, could be exploited to reduce the likelihood of successful L. rigidum establishment in the following season.
A double EPSPS gene mutation endowing glyphosate resistance shows a remarkably high resistance cost
Publisher: Wiley
Date: 06-10-2017
DOI: 10.1111/PCE.13067
Abstract: A novel glyphosate resistance double point mutation (T102I/P106S, TIPS) in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene has been recently identified for the first time only in the weed species Eleusine indica. Quantification of plant resistance cost associated with the TIPS and the often reported glyphosate resistance single P106S mutation was performed. A significant resistance cost (50% in seed number currency) associated with the homozygous TIPS but not the homozygous P106S EPSPS variant was identified in E. indica plants. The resistance cost associated with the TIPS mutation escalated to 85% in plants under resource competition with rice crops. The resistance cost was not detected in nonhomozygous TIPS plants denoting the recessive nature of the cost associated with the TIPS allele. An excess of 11-fold more shikimate and sixfold more quinate in the shikimate pathway was detected in TIPS plants in the absence of glyphosate treatment compared to wild type, whereas no changes in these compounds were observed in P106S plants when compared to wild type. TIPS plants show altered metabolite levels in several other metabolic pathways that may account for the expression of the observed resistance cost.
Glyphosate – How it Became a Once in a Hundred Year Herbicide and Its Future
Publisher: Research Information Ltd.
Date: 12-2018
DOI: 10.1564/V29_DEC_03
CROSS-RESISTANCE TO HERBICIDES IN ANNUAL RYEGRASS (LOLIUM-RIGIDUM) .2. CHLORSULFURON RESISTANCE INVOLVES A WHEAT-LIKE DETOXIFICATION SYSTEM
Publisher: Oxford University Press (OUP)
Date: 04-1991
DOI: 10.1104/PP.95.4.1036
Beyond modelling: considering user-centred and post-development aspects to ensure the success of a decision support system
Publisher: Elsevier BV
Date: 02-2016
Aldo‐keto reductase may contribute to glyphosate resistance in Lolium rigidum
Publisher: Wiley
Date: 28-12-2022
DOI: 10.1002/PS.7325
Abstract: We have previously demonstrated that an aldo‐keto reductase (AKR) from Echinochloa colona (EcAKR4‐1) can metabolize glyphosate and confers glyphosate resistance. This study aims to investigate if the EcAKR4‐1 orthologs from Lolium rigidum also play a role in glyphosate resistance in non‐target‐site based, glyphosate‐resistant (R) L. rigidum populations from Western Australia. The full‐length L. rigidum AKR gene ( LrAKR4C10 ) orthologous to EcAKR4‐1 , together with a distinct LrAKR1 , were cloned from plants of a glyphosate‐susceptible (S) (VLR1) and three glyphosate R L. rigidum populations (WALR50, WALR60 and WALR70). Reverse transcription quantitative polymerase chain reaction (RT‐qPCR) results showed that basal expression levels of the two LrAKR genes did not differ between the R and S populations, but their expression was significantly induced by glyphosate (up to 4.3‐fold) or 2,4‐D treatment (up to 3.4‐fold) in R populations. Escherichia coli cells transformed respectively with LrAKR4C10 and LrAKR1 were more tolerant to glyphosate. Rice ( Oryza sativa ) seedlings overexpressing each of the two LrAKR gene survived glyphosate rates that were lethal to the green fluorescence protein (GFP) control plants. Structural modeling predicts a similar way of glyphosate binding and detoxification by LrAKR4C10 and EcAKR4‐1, but an alternative way of glyphosate binding by LrAKR1. Relatively lower capacity of the two LrAKRs in conferring glyphosate resistance than the known EcAKR4‐1 was discussed in relation to structural interaction. Glyphosate‐induced higher expression of the two LrAKR genes in L. rigidum populations contributes to a moderate level of glyphosate resistance likely through enhanced glyphosate metabolism. The herbicide 2,4‐D can also induce the LrAKR expression, indicating the potential antagonistic effect of 2,4‐D to glyphosate. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
High Levels of Herbicide Resistance in Rigid Ryegrass (Lolium rigidum) in the Wheat Belt of Western Australia1
Publisher: Cambridge University Press (CUP)
Date: 04-2001
Glyphosate-Resistant Rigid Ryegrass (Lolium rigidum) Populations in the Western Australian Grain Belt
Publisher: Cambridge University Press (CUP)
Date: 03-2010
DOI: 10.1614/WT-09-054.1
Abstract: Glyphosate-resistance evolution in weeds is evident globally, especially in areas where transgenic glyphosate-resistant crops dominate. Resistance to glyphosate is currently known in 16 weed species, including rigid ryegrass in Australia. Following the first report of glyphosate resistance in 1998, there are now 78 documented glyphosate-resistant populations of rigid ryegrass in grain-growing regions of southern Australia. In some regions where glyphosate-resistance evolution has already occurred in rigid ryegrass, transgenic glyphosate-resistant canola was introduced in 2008, further highlighting the need to monitor glyphosate-resistance evolution in weeds. A rigid ryegrass population (WALR70) was collected in 2005 from a crop field in Esperance, Western Australia, after it had survived applications of glyphosate. Dose–response experiments confirmed resistance in the population, with the glyphosate rate resulting in 50% mortality (LD 50 ) for WALR70 being 11 times greater than that for a susceptible biotype. The WALR70 population also had low levels of resistance to some acetyl coenzyme A carboxylase (ACCase)- and acetolactate synthase (ALS)-inhibiting herbicides (diclofop, fluazifop, clodinafop, tralkoxydim, chlorsulfuron, and imazethapyr), but was susceptible to other herbicide modes of action, such as atrazine, trifluralin, and paraquat. Two other rigid ryegrass populations assessed in this study were also confirmed to be resistant to glyphosate. The increasing number of glyphosate-resistant rigid ryegrass populations in Australia is of concern to growers because of the importance of glyphosate in intensive cropping systems and the introduction of glyphosate-resistant canola to this region.
Evolved polygenic herbicide resistance in L olium rigidum by low‐dose herbicide selection within standing genetic variation
Publisher: Wiley
Date: 12-07-2012
Resistance and the herbicide resource: perceptions of Western Australian grain growers
Publisher: Elsevier BV
Date: 12-2002
Multiple herbicide‐resistant L olium rigidum (annual ryegrass) now dominates across the W estern A ustralian grain belt
Publisher: Wiley
Date: 02-01-2014
DOI: 10.1111/WRE.12068
Cross-resistance to prosulfocarb and triallate in pyroxasulfone-resistantLoliumrigidum
Publisher: Wiley
Date: 15-04-2013
DOI: 10.1002/PS.3516
Abstract: Plants can rapidly evolve resistance to herbicide in response to repeated selection. This study focuses on cross-resistance patterns observed in Lolium rigidum following pyroxasulfone recurrent selection. The parental MR (multiresistant) population following four generations of pyroxasulfone recurrent selection evolved cross-resistance to prosulfocarb and triallate. At the recommended label rate of prosulfocarb or triallate (2000 g ha(-1) ), the progeny selected four times with pyroxasulfone (MR4) displayed 58 and 35% plant survival respectively. One additional cycle of prosulfocarb selection increased the resistance level to both prosulfocarb and triallate in the population MR4-P1. Prosulfocarb resistance is yet to be reported in L. rigidum field populations. This study suggests that L. rigidum plants can rapidly evolve cross-resistance to several wheat-selective herbicides under recurrent selection of a single mode of action. Weed populations displaying broad-spectrum cross-resistance to several herbicide modes of action are increasing in frequency in intensive world agriculture. Proactive and integrated measures for resistance management need to be developed globally on appropriate herbicide use in crop rotations.
Diversity of α‐tubulin transcripts in Lolium rigidum
Publisher: Wiley
Date: 10-10-2020
DOI: 10.1002/PS.6109
Understanding Lolium rigidum Seeds: The Key to Managing a Problem Weed?
Publisher: MDPI AG
Date: 24-09-2012
Manipulating crop row orientation and crop density to suppress Lolium rigidum
Publisher: Wiley
Date: 26-09-2015
DOI: 10.1111/WRE.12180
Metribuzin Resistance in a Wild Radish (Raphanus raphanistrum) Population via Both psbA Gene Mutation and Enhanced Metabolism
Publisher: American Chemical Society (ACS)
Date: 14-01-2019
Abstract: There have been many studies on target-site resistance (TSR) to PSII-inhibiting herbicides, but only a few on the non-target-site resistance (NTSR). Here, we reported both TSR and NTSR to metribuzin in a wild radish population. Dose-response studies revealed a higher level of resistance to metribuzin in the resistant (R) compared to the susceptible (S) population. Sequencing of the target psbA gene revealed the known Ser-264-Gly mutation in R plants. In addition, a higher level of [
Photoinhibition of Photosynthesis Induced by Visible Light
Publisher: Annual Reviews
Date: 06-1984
Socially impaired robots: Human social disorders and robots’ socio-emotional intelligence
Publisher: Springer International Publishing
Date: 2014
Mechanism of Resistance to Chlorotoluron in Two Biotypes of the Grass Weed Alopecurus myosuroides
Publisher: Elsevier BV
Date: 11-1995
ABA inhibits germination but not dormancy release in mature imbibed seeds of Lolium rigidum Gaud.
Publisher: Oxford University Press (OUP)
Date: 06-2009
DOI: 10.1093/JXB/ERP175
An ABCC-type transporter endowing glyphosate resistance in plants
Publisher: Proceedings of the National Academy of Sciences
Date: 12-04-2021
Abstract: Glyphosate is the world’s dominantly used herbicide to control weedy plant species in a wide range of situations, especially in global field crops of soybean, maize, canola, and cotton with genetically engineered glyphosate resistance. Persistent glyphosate selection has led to worldwide evolution of glyphosate-resistant weeds. Several biochemical and physiological mechanisms have been identified that endow glyphosate resistance. To be toxic to plants, glyphosate must be present in the cytoplasm, and thus mechanisms reducing the cytoplasmic glyphosate to a sublethal level could confer resistance. Here, we provide evidence of a plant ABC transporter (ABCC8) that likely serves as a plasma membrane glyphosate exporter, lowering the cytoplasmic glyphosate level and thereby endowing glyphosate resistance.
On the Mechanism of Resistance to Paraquat in Hordeum glaucum and H. leporinum
Publisher: Oxford University Press (OUP)
Date: 10-1992
DOI: 10.1104/PP.100.2.630
Increased Carrier Volume Improves Preemergence Control of Rigid Ryegrass (Lolium rigidum) in Zero-Tillage Seeding Systems
Publisher: Cambridge University Press (CUP)
Date: 12-2013
Abstract: PRE herbicides are less effective in the zero-tillage system because of increased residual crop stubble and reduced soil incorporation. However, since weeds are not physically controlled in the zero-tillage system, reliance on efficacy of PRE herbicides is increased. This research investigated the impact of carrier volume and droplet size on the performance of PRE herbicides (in wheat crops at four sites in 2010) to improve herbicide efficacy in conditions of high stubble biomass in zero-tillage systems. Increasing carrier volume from 30 to 150 L ha −1 increased spray coverage on water-sensitive paper from an average of 5 to 32%. Average control of rigid ryegrass by trifluralin (at Cunderdin and Merredin sites) and trifluralin or pyroxasulfone (at Wickepin and Esperance sites) improved from 53 to 78% with increasing carrier volume. Use of ASABE Medium droplet size improved spray coverage compared with ASABE Extremely Coarse droplet size, but did not affect herbicide performance. It is clear that increased carrier volume improves rigid ryegrass weed control for nonwater-soluble (trifluralin) and water-soluble (pyroxasulfone) PRE herbicides. Western Australian growers often use low carrier volumes to reduce time of spray application or because sufficient high-quality water is not available, but the advantages of improved weed control justifies the use of a high carrier volume in areas of high weed density.
2,4-D resistance in wild radish: reduced herbicide translocation via inhibition of cellular transport
Publisher: Oxford University Press (OUP)
Date: 19-03-2016
DOI: 10.1093/JXB/ERW120
Evolution in Action: Plants Resistant to Herbicides
Publisher: Annual Reviews
Date: 02-06-2010
DOI: 10.1146/ANNUREV-ARPLANT-042809-112119
Abstract: Modern herbicides make major contributions to global food production by easily removing weeds and substituting for destructive soil cultivation. However, persistent herbicide selection of huge weed numbers across vast areas can result in the rapid evolution of herbicide resistance. Herbicides target specific enzymes, and mutations are selected that confer resistance-endowing amino acid substitutions, decreasing herbicide binding. Where herbicides bind within an enzyme catalytic site very few mutations give resistance while conserving enzyme functionality. Where herbicides bind away from a catalytic site many resistance-endowing mutations may evolve. Increasingly, resistance evolves due to mechanisms limiting herbicide reaching target sites. Especially threatening are herbicide-degrading cytochrome P450 enzymes able to detoxify existing, new, and even herbicides yet to be discovered. Global weed species are accumulating resistance mechanisms, displaying multiple resistance across many herbicides and posing a great challenge to herbicide sustainability in world agriculture. Fascinating genetic issues associated with resistance evolution remain to be investigated, especially the possibility of herbicide stress unleashing epigenetic gene expression. Understanding resistance and building sustainable solutions to herbicide resistance evolution are necessary and worthy challenges.
Initial characterisation of low and high seed dormancy populations of Lolium rigidum produced by repeated selection
Publisher: Elsevier BV
Date: 10-2010
DOI: 10.1016/J.JPLPH.2010.04.004
Abstract: The physiological and biochemical bases of seed dormancy in Lolium rigidum (annual ryegrass) are largely unknown, and study of this process is complicated by the outcrossing nature of the species and the strong influence of environment on seed dormancy. In order to identify heritable biochemical factors contributing to seed dormancy in L. rigidum, seeds from a field-collected population were used to select sub-populations with consistently low or high seed dormancy over four generations. Low-dormancy seeds showed constitutive alpha-amylase activity prior to imbibition, higher concentrations of polyphenols and cis-zeatin, and lower abscisic acid and cis-zeatin riboside concentrations than high-dormancy seeds. Selection for high dormancy was associated with a reduction in response to dark-stratification for 21d at 20 degrees C (an effective means of releasing dormancy in the original, unselected population) over successive generations, but fluridone remained effective in breaking dormancy. Crossing of low- and high-dormancy populations indicated that dormancy level was not dependent upon the maternal genotype of the seed, and that the constitutive alpha-amylase activity and high seed anthocyanin concentrations characteristic of the low-dormancy populations were not correlated to high basal germination ability.
RIM: a bioeconomic model for integrated weed management of Lolium rigidum in Western Australia
Publisher: Elsevier BV
Date: 03-2004
2,4-D and dicamba resistance mechanisms in wild radish: subtle, complex and population specific?
Publisher: Oxford University Press (OUP)
Date: 11-06-2018
DOI: 10.1093/AOB/MCY097
Genetic inheritance of cytochrome P450-mediated metabolic resistance to chlorsulfuron in a multiple herbicide resistant Lolium rigidum population
Publisher: Elsevier BV
Date: 11-2014
Widespread occurrence of both metabolic and target-site herbicide resistance mechanisms inLolium rigidumpopulations
Publisher: Wiley
Date: 25-03-2015
DOI: 10.1002/PS.3995
Abstract: Lolium rigidum populations in Australia and globally have demonstrated rapid and widespread evolution of resistance to acetyl coenzyme A carboxylase (ACCase)-inhibiting and acetolactate synthase (ALS)-inhibiting herbicides. Thirty-three resistant L. rigidum populations, randomly collected from crop fields in a most recent resistance survey, were analysed for non-target-site diclofop metabolism and all known target-site ACCase gene resistance-endowing mutations. The HPLC profile of [(14) C]-diclofop-methyl in vivo metabolism revealed that 79% of these resistant L. rigidum populations showed enhanced capacity for diclofop acid metabolism (metabolic resistance). ACCase gene sequencing identified that 91% of the populations contain plants with ACCase resistance mutation(s). Importantly, 70% of the populations exhibit both non-target-site metabolic resistance and target-site ACCase mutations. This work demonstrates that metabolic herbicide resistance is commonly occurring in L. rigidum, and coevolution of both metabolic resistance and target-site resistance is an evolutionary reality. Metabolic herbicide resistance can potentially endow resistance to many herbicides and poses a threat to herbicide sustainability and thus crop production, calling for major research and management efforts.
Intensive cropping systems select for greater seed dormancy and increased herbicide resistance levels in Lolium rigidum (annual ryegrass)
Publisher: Wiley
Date: 04-09-2014
DOI: 10.1002/PS.3874
Abstract: Lolium rigidum (annual ryegrass) is a widespread annual crop weed that has evolved high levels of resistance to selective herbicides. Anecdotal evidence suggests that intensive cropping also leads to higher seed dormancy in L. rigidum. This was quantified by measuring dormancy levels in L. rigidum populations collected from paired sites (one with nil to low cropping intensity, the other intensively cropped) located throughout the Western Australian grain belt. Populations from non-cropped fields or those with low cropping intensity showed higher and faster germination than populations from fields with a medium- or high-intensity cropping regime. Resistance to selective herbicides was also higher in the medium- and high-intensity cropping fields than in the low-intensity cropping fields. High-intensity cropping systems are likely to impose greater selection pressures for seed dormancy and selective herbicide resistance, because late-emerging seedlings avoid preplanting weed control practices (tillage and non-selective herbicide application) but are exposed to selective in-crop herbicides.
Resistance to Acetyl-Coenzyme a Carboxylase-Inhibiting Herbicides Endowed by a Single Major Gene Encoding a Resistant Target Site in a Biotype of Lolium rigidum
Publisher: CSIRO Publishing
Date: 1996
DOI: 10.1071/PP9960015
Abstract: The mechanism and mode of inheritance of resistance to acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides was investigated in a biotype of Lolium rigidum that has evolved resistance following selection with diclofop-methyl for 10 consecutive years. ACCase extracted from the resistant biotype is 6.9 times more resistant to inhibition by diclofop than enzyme from a susceptible biotype. Similar or greater levels of resistance were found to other related herbicides. There is no difference in absorption or metabolism of diclofop-methyl or haloxyfop-methyl between the resistant and susceptible biotypes, hence differential absorption or metabolism of these herbicides does not contribute to resistance. F1 families from reciprocal crosses between the resistant biotype and a susceptible biotype respond similarly to the herbicide and are nearly as resistant as the resistant parent, indicating that the resistance trait is nuclearly located and has incomplete dominance over susceptibility. F2 families treated with 26 and 208 g ai ha-1 of haloxyfop-ethoxyethyl reveal only two phenotypes: resistant plants showing no injury and susceptible plants showing no growth. At both rates of haloxyfop-ethoxyethyl, the segregation of resistance to susceptibility follows a ratio of 3:1 (R:S) that fits the predicted ratio for a single nuclear gene with high dominance. From the F1 and F2 data, it is concluded that resistance to haloxyfop in this resistant biotype of L. rigidum is inherited as a single nuclear incompletely dominant gene coding for a resistant form of the target enzyme ACCase.
Novel α-Tubulin Mutations Conferring Resistance to Dinitroaniline Herbicides in Lolium rigidum
Publisher: Frontiers Media SA
Date: 06-02-2018
Evolved glyphosate‐resistant weeds around the world: lessons to be learnt
Publisher: Wiley
Date: 13-02-2008
DOI: 10.1002/PS.1525
Abstract: Glyphosate is the world's most important herbicide, with many uses that deliver effective and sustained control of a wide spectrum of unwanted (weedy) plant species. Until recently there were relatively few reports of weedy plant species evolving resistance to glyphosate. Since 1996, the advent and subsequent high adoption of transgenic glyphosate-resistant crops in the Americas has meant unprecedented and often exclusive use of glyphosate for weed control over very large areas. Consequently, in regions of the USA where transgenic glyphosate-resistant crops dominate, there are now evolved glyphosate-resistant populations of the economically damaging weed species Ambrosia artemissifolia L., Ambrosia trifida L., Amaranthus palmeri S Watson, Amaranthus rudis JD Sauer, Amaranthus tuberculatus (Moq) JD Sauer and various Conyza and Lolium spp. Likewise, in areas of transgenic glyphosate-resistant crops in Argentina and Brazil, there are now evolved glyphosate-resistant populations of Sorghum halepense (L.) Pers and Euphorbia heterophylla L. respectively. As transgenic glyphosate-resistant crops will remain very popular with producers, it is anticipated that glyphosate-resistant biotypes of other prominent weed species will evolve over the next few years. Therefore, evolved glyphosate-resistant weeds are a major risk for the continued success of glyphosate and transgenic glyphosate-resistant crops. However, glyphosate-resistant weeds are not yet a problem in many parts of the world, and lessons can be learnt and actions taken to achieve glyphosate sustainability. A major lesson is that maintenance of ersity in weed management systems is crucial for glyphosate to be sustainable. Glyphosate is essential for present and future world food production, and action to secure its sustainability for future generations is a global imperative.
Herbicide resistance-endowing ACCase gene mutations in hexaploid wild oat (Avena fatua): insights into resistance evolution in a hexaploid species
Publisher: Springer Science and Business Media LLC
Date: 10-10-2012
DOI: 10.1038/HDY.2012.69
Management of herbicide resistance in wheat cropping systems: learning from the Australian experience
Publisher: Wiley
Date: 20-01-2014
DOI: 10.1002/PS.3704
Abstract: Herbicide resistance continues to escalate in weed populations infesting global wheat (Triticum aestivum L.) crops, threatening grain production and thereby food supply. Conservation wheat production systems are reliant on the use of efficient herbicides providing low-cost, selective weed control in intensive cropping systems. The resistance-driven loss of herbicide resources combined with limited potential for new herbicide molecules means greater emphasis must be placed on preserving existing herbicides. For more than two decades, since the initial recognition of the dramatic consequences of herbicide resistance, the challenge of introducing additional weed control strategies into herbicide-based weed management programmes has been formidable. Throughout this period, herbicide resistance has expanded unabated across the world's wheat production regions. However, in Australia, where herbicide resources have become desperately depleted, the adoption of harvest weed seed control is evidence, at last, of a successful approach to sustainable weed management in wheat production systems. Growers routinely including strategies to target weed seeds during crop harvest, as part of herbicide-based weed management programmes, are now realising significant weed control and crop production benefits. When combined with an attitude of zero weed tolerance, there is evidence of a sustainable weed control future for wheat production systems. The hard-learned lessons of Australian growers can now be viewed by global wheat producers as an ex le of how to stop the continual loss of herbicide resources in productive cropping systems.
Salsola tragus or S. australis (Chenopodiaceae) in Australia—untangling taxonomic confusion through molecular and cytological analyses
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/BT08043
Abstract: Salsola tragus sensu lato (Chenopodiaceae) is found throughout Western Australia and is considered to be a weed in both natural and agricultural ecosystems, although the current taxonomic status of this species is not clear. The taxonomic literature reports morphological variation within Australian populations of the weed, indicating that there may be genetically distinct ecotypes or unidentified subspecies present within the species. A genetic and cytological approach was used to detect variation between 22 populations of S. tragus sensu lato in the south-west of Western Australia. Out-groups used in this study included a population of S. tragus L. from the USA and Maireana brevifolia (R.Br.) Paul G.Wilson (Chenopodiaceae) from Lake Grace. Four genetically distinct groups were identified, which were not closely related to the S. tragus out-group (~60% similarity). Further, these groups and a S. australis R.Br. s le from the USA were all diploid (2n = 18), unlike the tetraploid (2n = 36) S. tragus. The predominant wheatbelt weed, group A, which was previously classified as S. tragus ssp. tragus L., was identified as S. australis. This species is probably native to Australia, given its arrival predated European invasion. Further research is required to clarify the taxonomic status of the other three possible taxa and determine their status in relation to S. australis.
Perceiving forces, bumps, and touches from proprioceptive expectations
Publisher: Springer Berlin Heidelberg
Date: 2012
Glyphosate, paraquat and ACCase multiple herbicide resistance evolved in a Lolium rigidum biotype
Publisher: Springer Science and Business Media LLC
Date: 12-08-2006
DOI: 10.1007/S00425-006-0364-3
Abstract: Glyphosate is the world's most widely used herbicide. A potential substitute for glyphosate in some use patterns is the herbicide paraquat. Following many years of successful use, neither glyphosate nor paraquat could control a biotype of the widespread annual ryegrass (Lolium rigidum), and here the world's first case of multiple resistance to glyphosate and paraquat is confirmed. Dose-response experiments established that the glyphosate rate causing 50% mortality (LD(50)) for the resistant (R) biotype is 14 times greater than for the susceptible (S) biotype. Similarly, the paraquat LD(50 )for the R biotype is 32 times greater than for the S biotype. Thus, based on the LD(50 )R/S ratio, this R biotype of L. rigidum is 14-fold resistant to glyphosate and 32-fold resistant to paraquat. This R biotype also has evolved resistance to the acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of paraquat resistance in this biotype was determined as restricted paraquat translocation. Resistance to ACCase-inhibiting herbicides was determined as due to an insensitive ACCase. Two mechanisms endowing glyphosate resistance were established: firstly, a point mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, resulting in an amino acid substitution of proline to alanine at position 106 secondly, reduced glyphosate translocation was found in this R biotype, indicating a co-occurrence of two distinct glyphosate resistance mechanisms within the R population. In total, this R biotype displays at least four co-existing resistance mechanisms, endowing multiple resistance to glyphosate, paraquat and ACCase herbicides. This alarming case in the history of herbicide resistance evolution represents a serious challenge for the sustainable use of the precious agrochemical resources such as glyphosate and paraquat.
The economic value of pasture phases in the integrated management of annual ryegrass and wild radish in a Western Australian farming system
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/EA03050
Abstract: Most cropping farms in Western Australia must deal with the management of herbicide-resistant populations of weeds such as annual ryegrass (Lolium rigidum Gaudin) and wild radish (Raphanus raphanistrum�L.). Farmers are approaching the problem of herbicide resistance by adopting integrated weed management systems, which allow weed control with a range of different techniques. One important question in the design of such systems is whether and when the benefits of including pasture in rotation with crops exceed the costs. In this paper, the multi-species resistance and integrated management model was used to investigate the value of including pasture phases in the crop rotation. The most promising of the systems examined appears to be so-called 'phase farming', involving occasional 3-year phases of pasture rather than shorter, more frequent and regular pasture phases. This approach was competitive with the best continuous cropping rotation in a number of scenarios, particularly where herbicide resistance was at high levels.
Gene amplification delivers glyphosate-resistant weed evolution
Publisher: Proceedings of the National Academy of Sciences
Date: 11-01-2010
Hybridisation between Brassica napus L. and Raphanus raphanistrum L. under agronomic field conditions
Publisher: Springer Science and Business Media LLC
Date: 09-2001
DOI: 10.1007/PL00002909
High Seed Retention at Maturity of Annual Weeds Infesting Crop Fields Highlights the Potential for Harvest Weed Seed Control
Publisher: Cambridge University Press (CUP)
Date: 09-2014
Abstract: Seed production of annual weeds persisting through cropping phases replenishes/establishes viable seed banks from which these weeds will continue to interfere with crop production. Harvest weed seed control (HWSC) systems are now viewed as an effective means of interrupting this process by targeting mature weed seed, preventing seed bank inputs. However, the efficacy of these systems is directly related to the proportion of total seed production that the targeted weed species retains (seed retention) at crop maturity. This study determined the seed retention of the four dominant annual weeds of Australian cropping systems - annual ryegrass, wild radish, brome grass, and wild oat. Beginning at the first opportunity for wheat harvest and on a weekly basis for 28 d afterwards the proportion of total seed production retained above a 15 cm harvest cutting height was determined for these weed species present in wheat crops at nine locations across the Western Australian (WA) wheat-belt. Very high proportions of total seed production were retained at wheat crop maturity for annual ryegrass (85%), wild radish (99%), brome grass (77%), and wild oat (84%). Importantly, seed retention remained high for annual ryegrass and wild radish throughout the 28 d harvest period. At the end of this period, 63 and 79% of total seed production for annual ryegrass and wild radish respectively, was retained above harvest cutting height. However, seed retention for brome grass (41%) and wild oat (39%) was substantially lower after 28 d. High seed retention at crop maturity, as identified here, clearly indicates the potential for HWSC systems to reduce seed bank replenishment and diminish subsequent crop interference by the four most problematic species of Australian crops.
A Val‐202‐Phe α‐tubulin mutation and enhanced metabolism confer dinitroaniline resistance in a single Lolium rigidum population
Publisher: Wiley
Date: 15-08-2019
DOI: 10.1002/PS.5561
Abstract: A Lolium rigidum population collected from Western Australia was previously reported as highly resistant to dinitroaniline herbicides mainly due to a Val-202-Phe substitution in the target site α-tubulin protein. To further determine the contribution of the 202 mutation to resistance, two sub-populations, respectively comprising the 202 mutant and wild-type (WT) in iduals, were isolated from within the same resistant population and subject to dinitroaniline herbicide doses. A rice transgenic study was conducted to demonstrate whether the amino acid substitution at the 202 residue confers resistance. In addition, as indicated in the phenotyping and genotyping study, non-target enhanced trifluralin metabolism was further examined in the same population. The 202 mutants were more resistant than the wild-type plants. Rice calli transformed with the L. rigidum mutant α-tubulin gene (Val-202-Phe) were more resistant to dinitroaniline herbicides relative to calli transformed with the wild-type gene. Also, enhanced trifluralin metabolism was detected in the 202 mutants in comparison to the susceptible seedlings. Both target-site Val-202-Phe α-tubulin mutation and non-target-site enhanced trifluralin metabolism co-exist in this dinitroaniline-resistant L. rigidum population. © 2019 Society of Chemical Industry.
Herbicide‐resistant weeds: from research and knowledge to future needs
Publisher: Wiley
Date: 10-09-2013
DOI: 10.1111/EVA.12098
A dinitroaniline herbicide resistance mutation can be nearly lethal to plants
Publisher: Wiley
Date: 21-01-2022
DOI: 10.1002/PS.6773
Abstract: Lolium rigidum is the most important weed in Australian agriculture and pre‐emergence dinitroaniline herbicides (e.g., trifluralin) are widely and persistently used for Lolium control. Consequently, evolution of resistance to dinitroaniline herbicides has been increasingly reported. Resistance‐endowing target‐site α‐tubulin gene mutations are identified with varying frequency. This study investigated the putative fitness cost associated with the common resistance mutation Val–202–Phe and the rare resistance mutation Arg–243–Met causing helical plant growth. Results showed a deleterious effect of Arg–243–Met on fitness when plants are homozygous for this mutation. This was evidenced as high plant mortality, severely diminished root and aboveground vegetative growth (lower relative growth rate), and very poor fecundity compared with the wild‐type, which led to a nearly lethal fitness cost of .9% in competition with a wheat crop. A fitness penalty in vegetative growth was evident, but to a much lesser extent, in plants heterozygous for the Arg–243–Met mutation. By contrast, plants possessing the Val–202–Phe mutation exhibited a fitness advantage in vegetative and reproductive growth. The α‐tubulin mutations Arg–243–Met and Val–202–Phe have contrasting effects on fitness. These results help understand the absence of plants homozygous for the Arg–243–Met mutation and the high frequency of plants carrying the Val–202–Phe mutation in dinitroaniline‐resistant L. rigidum populations. The α‐tubulin Arg–243–Met mutation can have an exceptional fitness cost with nearly lethal effects on resistant L. rigidum plants. © 2022 Society of Chemical Industry.
Identification of the first glyphosate‐resistant wild radish (Raphanus raphanistrum L.) populations
Publisher: Wiley
Date: 15-05-2014
DOI: 10.1002/PS.3815
Abstract: In Australia, glyphosate has been used routinely to control wild radish (Raphanus raphanistrum L.) for the past 40 years. This study focuses on two field-evolved glyphosate-resistant populations of wild radish collected from the grainbelt of Western Australia. Two wild radish biotypes were confirmed to be glyphosate resistant by comparing R/S of two suspected populations. Based on R/S from dose-response curves, the R1 and R2 populations were 2.3 and 3.2 times more resistant to glyphosate respectively. Dose response on glyphosate-selected progeny (>1080 g ha(-1)) demonstrated that the glyphosate resistance mechanism was heritable. When compared with the pooled mortality results of three known susceptible populations (S1, S2 and S3), the R1 and R2 subpopulations were 3.4-fold and 4.5-fold more resistant at the LD50 level respectively. Both populations were found to have multiple resistance to the phytoene desaturase inhibitor diflufenican, the synthetic auxin 2,4-D and the ALS inhibitors chlorsulfuron, sulfometuron-methyl, imazethapyr and metosulam. This is the first report confirming glyphosate resistance evolution in wild radish and serves to re-emphasise the importance of erse weed control strategies. Proactive and integrated measures for resistance management need to be developed to ersify control measures away from glyphosate and advance the use of non-herbicidal techniques.
Herbicide Resistance in Rigid Ryegrass (Lolium rigidum)Has Not Led to Higher Weed Densities in Western Australian Cropping Fields
Publisher: Cambridge University Press (CUP)
Date: 02-2009
DOI: 10.1614/WS-08-067.1
Abstract: The aim of this study was to test whether herbicide resistance in rigid ryegrass has led to increased densities of this weed in Western Australian (WA) cropping fields. A total of 503 wheat fields with previously unknown management history and weed status were visited prior to harvest across 15 agronomic areas of the central WA cropping belt in 1998 and 2003. Rigid ryegrass density was visually assessed and, where possible, seed was collected from the population. Ryegrass was found in 91% of the wheat crops s led. Ryegrass populations were tested in the following year for resistance to chlorsulfuron, sulfometuron, diclofop, and clethodim. With the use of nonparametric and regression statistical methods, resistance status, including multiple-resistance status, was not found to be associated with higher weed density. The results show that growers are generally maintaining low densities in fields with herbicide-resistant rigid ryegrass. The most common rigid ryegrass density at harvest time was less than 1 plant m −2 in both resistant and susceptible populations. Field and model-based studies of weed and herbicide resistance management that allow populations to continue at very high densities are unlikely to reflect common grower practice.
Glyphosate: a once‐in‐a‐century herbicide
Publisher: Wiley
Date: 13-12-2016
DOI: 10.1002/PS.1518
Abstract: Since its commercial introduction in 1974, glyphosate [N-(phosphonomethyl)glycine] has become the dominant herbicide worldwide. There are several reasons for its success. Glyphosate is a highly effective broad-spectrum herbicide, yet it is very toxicologically and environmentally safe. Glyphosate translocates well, and its action is slow enough to take advantage of this. Glyphosate is the only herbicide that targets 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS), so there are no competing herbicide analogs or classes. Since glyphosate became a generic compound, its cost has dropped dramatically. Perhaps the most important aspect of the success of glyphosate has been the introduction of transgenic, glyphosate-resistant crops in 1996. Almost 90% of all transgenic crops grown worldwide are glyphosate resistant, and the adoption of these crops is increasing at a steady pace. Glyphosate/glyphosate-resistant crop weed management offers significant environmental and other benefits over the technologies that it replaces. The use of this virtually ideal herbicide is now being threatened by the evolution of glyphosate-resistant weeds. Adoption of resistance management practices will be required to maintain the benefits of glyphosate technologies for future generations.
Risks of gene flow from transgenic herbicide-resistant canola (Brassica napus) to weedy relatives in southern Australian cropping systems
Publisher: CSIRO Publishing
Date: 1999
DOI: 10.1071/A97138
Abstract: It is likely that transgenic canola expressing genes encoding resistance to glyphosate and glufosinate ammonium will be introduced into the Australian cropping system in the next few years. One risk associated with the introduction of such cultivars is the release of herbicide resistance genes into weedy relatives of canola. This review examines the currently available experimental information regarding the possibility of gene flow from canola to weedy relatives. Three species are identified as having the potential to outcross with canola, Brassica juncea, B. rapa, and Raphanus raphanistrum. Two of these species are not yet widespread weeds of the southern Australian cropping zone. In contrast, R. raphanistrum is already a major weed in Australia with existing resistance to ALS-inhibiting herbicides. Information is urgently needed to determine whether successful hybrids between B. napus and R. raphanistrum can be produced under Australian conditions. Major deficiencies in the existing information are identified in relation to some other important weed species within the southern Australian cropping zone. Further studies are required to determine the out-crossing potential of canola to B. tournefortii, Diplotaxis tenuifolia, Sisymbrium officinale, and S. orientale if transgenic canola is to be safely and responsibly introduced into Australia.
Design Methodology for the UX of HRI: A Field Study of a Commercial Social Robot at an Airport
Publisher: ACM
Date: 26-02-2018
Real-time human-robot interactive coaching system with full-body control interface
Publisher: Springer Berlin Heidelberg
Date: 2012
AHAS herbicide resistance endowing mutations: effect on AHAS functionality and plant growth
Publisher: Oxford University Press (OUP)
Date: 13-07-2010
DOI: 10.1093/JXB/ERQ205
Rapid Evolution of Herbicide Resistance by Low Herbicide Dosages
Publisher: Cambridge University Press (CUP)
Date: 06-2011
Abstract: Herbicide rate cutting is an ex le of poor use of agrochemicals that can have potential adverse implications due to rapid herbicide resistance evolution. Recent laboratory-level studies have revealed that herbicides at lower-than-recommended rates can result in rapid herbicide resistance evolution in rigid ryegrass populations. However, crop-field-level studies have until now been lacking. In this study, we examined the impact of low rates of diclofop on the evolution of herbicide resistance in a herbicide-susceptible rigid ryegrass population grown either in a field wheat crop or in potted plants maintained in the field. Subsequent dose–response profiles indicated rapid evolution of diclofop resistance in the selected rigid ryegrass lines from both the crop-field and field pot studies. In addition, there was moderate level of resistance in the selected lines against other tested herbicides to which the population has never been exposed. This resistance evolution was possible because low rates of diclofop allowed substantial rigid ryegrass survivors due to the potential in this cross-pollinated species to accumulate all minor herbicide resistance traits present in the population. The practical lesson from this research is that herbicides should be used at the recommended rates that ensure high weed mortality to minimize the likelihood of minor herbicide resistance traits leading to rapid herbicide resistance evolution.
Herbicide resistance and the adoption of integrated weed management by Western Australian grain growers
Publisher: Wiley
Date: 2007
Non-target site mechanism of metribuzin tolerance in induced tolerant mutants of narrow-leafed lupin (Lupinus angustifolius L.)
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/CP12065
Abstract: Narrow-leafed lupin (Lupinus angustifolius L.) is an important grain legume crop in Australia. Metribuzin is an important herbicide used to control weeds in lupin crops. This study investigated metribuzin tolerance mechanism in narrow-leafed lupin by comparing two induced mutants (Tanjil-AZ-33 and Tanjil-AZ-55) of higher metribuzin tolerance with the susceptible wild type. Sequencing of the highly conserved region of the chloroplast psbA gene (target site) revealed that the sequences of the wild type and the mutants were identical and therefore metribuzin tolerance is not target site based. Photosynthetic activity was measured and the leaf photosynthesis of the two tolerant mutants was initially inhibited after metribuzin treatment, but recovered within 2.5 days whereas that of the susceptible plants remained inhibited. The photosynthetic measurements confirmed the target site chloroplast was susceptible and the tolerance mechanism is non-target site based. Investigation with known cytochrome P450 monooxygenase inhibitors (omethoate, malathion and phorate) showed that tolerance could be reversed in both mutants, indicating the tolerance mechanism in two tolerant mutants may involve cytochrome P450 enzymes. Interestingly, the inhibitor tridiphane reversed metribuzin tolerance of only one of the two tolerant mutants, indicating ersity in metribuzin tolerance mechanisms in narrow-leafed lupin. These results signify that further investigation of metribuzin metabolism in these plants is warranted. In conclusion, metribuzin tolerance mechanism in lupin mutants is non-target site based, likely involving P450-mediated metribuzin metabolism.
Widespread occurrence of multiple herbicide resistance in Western Australian annual ryegrass (Lolium rigidum) populations
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/AR06283
Abstract: In 2003, a random survey was conducted across the Western Australian wheatbelt to establish the frequency and distribution of herbicide resistance in ryegrass populations infesting crop fields. Five hundred cropping fields were visited at crop maturity, and ryegrass seed was collected in 452 of these fields. Subsequently, each crop field population was screened with herbicides of various modes of action that are commonly used for ryegrass control in Australian cropping systems. Most of these ryegrass populations were found to be resistant to the ACCase-inhibitor herbicide diclofop-methyl (68%) and the ALS-inhibitor herbicide sulfometuron (88%). A comparison of resistance levels in the same agronomic zones surveyed 5 years earlier determined that there had been an increase of 20 percentage points in the frequency of resistance over this 5-year period. This survey also determined that the majority (64%) of populations were found to be multiple resistant to both diclofop-methyl and sulfometuron. The distribution patterns of the collected populations indicated that there were higher frequencies of resistant and developing resistance populations occurring in the intensively cropped regions of the wheatbelt, which had greater herbicide selection pressure. Of concern is that 24% and 8% of populations were found to be developing resistance to trifluralin and clethodim, respectively. Currently these herbicides are heavily relied upon for control of ACCase and ALS herbicide resistant ryegrass. Nearly all populations remain susceptible to glyphosate. Ryegrass across the WA wheatbelt now exhibits multiple resistance across many but not all herbicides, posing severe management and sustainability challenges.
Evidence for an ecological cost of enhanced herbicide metabolism in Lolium rigidum
Publisher: Wiley
Date: 16-06-2009
No auxinic herbicide–resistance cost in wild radish (Raphanus raphanistrum)
Publisher: Cambridge University Press (CUP)
Date: 14-08-2019
DOI: 10.1017/WSC.2019.40
Abstract: Wild radish ( Raphanus raphanistrum L.) is a problematic and economically damaging dicotyledonous weed infesting crops in many regions of the world. Resistance to the auxinic herbicides 2,4-D and dicamba is widespread in Western Australian R. raphanistrum populations, with the resistance mechanism appearing to involve alterations in the physiological response to synthetic auxins and in plant defense. This study aimed to determine whether these alterations cause inhibition in plant growth or reproduction that could potentially be exploited to manage 2,4-D–resistant populations in cropping areas. Therefore, the morphology and seed production of resistant and susceptible populations were compared in an outdoor pot study, with plants grown in the presence and absence of competition by wheat ( Triticum aestivum L.). The susceptible and resistant R. raphanistrum populations were equally suppressed by wheat competition, with plant growth and seed production being decreased by approximately 50%. Although resistant populations produced less vegetative biomass than susceptible populations, there was no negative association between resistance and seed production. Therefore, it is unlikely that any nonherbicidal management practices will be more efficacious on 2,4-D–resistant than 2,4-D–susceptible R. raphanistrum populations.
Glyphosate resistance in perennial Sorghum halepense (Johnsongrass), endowed by reduced glyphosate translocation and leaf uptake
Publisher: Wiley
Date: 23-09-2011
DOI: 10.1002/PS.2286
Abstract: In a large cropping area of northern Argentina, Sorghum halepense (Johnsongrass) has evolved towards glyphosate resistance. This study aimed to determine the molecular and biochemical basis conferring glyphosate resistance in this species. Experiments were conducted to assess target EPSPS gene sequences and (14)C-glyphosate leaf absorption and translocation to meristematic tissues. In iduals of all resistant (R) accessions exhibited significantly less glyphosate translocation to root (11% versus 29%) and stem (9% versus 26%) meristems when compared with susceptible (S) plants. A notably higher proportion of the applied glyphosate remained in the treated leaves of R plants (63%) than in the treated leaves of S plants (27%). In addition, in iduals of S. halepense accession R(2) consistently showed lower glyphosate absorption rates in both adaxial (10-20%) and abaxial (20-25%) leaf surfaces compared with S plants. No glyphosate resistance endowing mutations in the EPSPS gene at Pro-101-106 residues were found in any of the evaluated R accessions. The results of the present investigation indicate that reduced glyphosate translocation to meristems is the primary mechanism endowing glyphosate resistance in S. halepense from cropping fields in Argentina. To a lesser extent, reduced glyphosate leaf uptake has also been shown to be involved in glyphosate-resistant S. halepense.
Be More Transparent and Users Will Like You: A Robot Privacy and User Experience Design Experiment
Publisher: ACM
Date: 26-02-2018
Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum
Publisher: Springer Science and Business Media LLC
Date: 29-09-2010
DOI: 10.1038/HDY.2010.124
Cinmethylin controls multiple herbicide‐resistant Lolium rigidum and its wheat selectivity is P450‐based
Publisher: Wiley
Date: 28-02-2020
DOI: 10.1002/PS.5798
Upgrading the RIM Model for Improved Support of Integrated Weed Management Extension Efforts in Cropping Systems
Publisher: Cambridge University Press (CUP)
Date: 12-2014
Abstract: RIM, or “Ryegrass Integrated Management,” is a user-friendly weed management software that integrates long-term economics. As a model-based decision support system, RIM enables users to easily build 10-year cropping scenarios and evaluate the impacts of management choices on annual rigid ryegrass populations and long-term profitability. Best used in a workshop format to enable learning through interactions, RIM can provide insights for the sustainable management of ryegrass through “what-if” scenarios in regions facing herbicide resistance issues. The upgrade of RIM is presented, with changes justified from an end-user perspective. The implementation of the model in a new, intuitive software format is presented, as well as the revision, update, and documentation of over 40 management options. Enterprises, establishment systems, and control options were redefined to represent current practices, with the notable inclusion of customizable herbicide options and techniques for weed seed control at harvest. Several ex les of how RIM can be used with farmers to demonstrate the benefits of adopting recommended practices for managing or delaying the onset of herbicide resistance are presented. Originally designed for the dryland broadacre systems of the Australian southern grainbelt, RIM's underlying modeling was restructured to facilitate future updates and adaptation to other weed species and cropping regions.
Molecular characterisation of resistance to ALS‐inhibiting herbicides in Hordeum leporinum biotypes
Publisher: Wiley
Date: 30-07-2007
DOI: 10.1002/PS.1429
Abstract: The acetolactate synthase (ALS)-inhibiting herbicide sulfosulfuron is registered in Australia for the selective control of Hordeum leporinum Link. in wheat crops. This herbicide failed to control H. leporinum on two farms in Western Australia on its first use. This study aimed to determine the level of resistance of three H. leporinum biotypes, identify the biochemical and molecular basis and develop molecular markers for diagnostic analysis of the resistance. Dose-response studies revealed very high level (>340-fold) resistance to the sulfonylurea herbicides sulfosulfuron and sulfometuron. In vitro ALS assays revealed that resistance was due to reduced sensitivity of the ALS enzyme to herbicide inhibition. This altered ALS sensitivity in the resistant biotypes was found to be due to a mutation in the ALS gene resulting in amino acid proline to serine substitution at position 197. In addition, two- to threefold higher ALS activities were consistently found in the resistant biotypes, compared with the known susceptible biotype. Two cleaved lified polymorphic sequence (CAPS) markers were developed for diagnostic testing of the resistant populations. This study established the first documented case of evolved ALS inhibitor resistance in H. leporinum and revealed that the molecular basis of resistance is due to a Pro to Ser mutation in the ALS gene.
Management Strategies for Herbicide-resistant Weed Populations in Australian Dryland Crop Production Systems
Publisher: Cambridge University Press (CUP)
Date: 04-2007
DOI: 10.1614/WT-06-086.1
RESISTANCE TO ACETOLACTATE SYNTHASE-INHIBITING HERBICIDES IN ANNUAL RYEGRASS (LOLIUM-RIGIDUM) INVOLVES AT LEAST 2 MECHANISMS
Publisher: Oxford University Press (OUP)
Date: 12-1992
The altruistic robot: Do what i want, not just what i say
Publisher: Springer International Publishing
Date: 2017
Mechanisms and Agronomic Aspects of Herbicide Resistance
Publisher: Annual Reviews
Date: 06-1993
Selection for low or high primary dormancy in Lolium rigidum Gaud seeds results in constitutive differences in stress protein expression and peroxidase activity
Publisher: Oxford University Press (OUP)
Date: 25-10-2011
DOI: 10.1093/JXB/ERQ334
Identity and Activity of 2,4-Dichlorophenoxyacetic Acid Metabolites in Wild Radish (Raphanus raphanistrum)
Publisher: American Chemical Society (ACS)
Date: 05-12-2018
Abstract: Synthetic auxin herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), are widely used for selective control of broadleaf weeds in cereals and transgenic crops. Although the troublesome weed wild radish ( Raphanus raphanistrum) has developed resistance to 2,4-D, no populations have yet displayed an enhanced capacity for metabolic detoxification of the herbicide, with both susceptible and resistant wild radish plants readily metabolizing 2,4-D. Using mass spectrometry and nuclear magnetic resonance, the major 2,4-D metabolite was identified as the glucose ester, and its structure was confirmed by synthesis. As expected, both the endogenous and synthetic compounds retained auxin activity in a bioassay. The lack of detectable 2,4-D hydroxylation in wild radish and the lability of the glucose ester suggest that metabolic 2,4-D resistance is unlikely to develop in this species.
My view
Publisher: Cambridge University Press (CUP)
Date: 07-2003
Photoinhibition of photosynthesis: effect on chlorophyll fluorescence at 77K in intact leaves and in chloroplast membranes of Nerium oleander
Publisher: Springer Science and Business Media LLC
Date: 11-1982
DOI: 10.1007/BF00395424
Cross‐resistance to prosulfocarb + S‐metolachlor and pyroxasulfone selected by either herbicide in Lolium rigidum
Publisher: Wiley
Date: 21-03-2016
DOI: 10.1002/PS.4253
Abstract: Weeds can be a greater constraint to crop production than animal pests and pathogens. Pre-emergence herbicides are crucial in many cropping systems to control weeds that have evolved resistance to selective post-emergence herbicides. In this study we assessed the potential to evolve resistance to the pre-emergence herbicides prosulfocarb + S-metolachlor or pyroxasulfone in 50 in idual field Lolium rigidum populations collected in a random survey in Western Australia prior to commercialisation of these pre-emergence herbicides. This study shows for the first time that in randomly collected L. rigidum field populations the selection with either prosulfocarb + S-metolachlor or pyroxasulfone can result in concomitant evolution of resistance to both prosulfocarb + S-metolachlor and pyroxasulfone after three generations. In the major weed L. rigidum, traits conferring resistance to new herbicides can be present before herbicide commercialisation. Proactive and multidisciplinary research (evolutionary ecology, modelling and molecular biology) is required to detect and analyse resistant populations before they can appear in the field. Several studies show that evolved cross-resistance in weeds is complex and often unpredictable. Thus, long-term management of cross-resistant weeds must be achieved through heterogeneity of selection by effective chemical, cultural and physical weed control strategies that can delay herbicide resistance evolution. © 2016 Society of Chemical Industry.
Multispecies resistance and integrated management: a bioeconomic model for integrated management of rigid ryegrass (Lolium rigidum) and wild radish (Raphanus raphanistrum)
Publisher: Cambridge University Press (CUP)
Date: 09-2003
DOI: 10.1614/P2002-118
Prior hydration of Brassica tournefortii seeds reduces the stimulatory effect of karrikinolide on germination and increases seed sensitivity to abscisic acid
Publisher: Oxford University Press (OUP)
Date: 25-03-2010
DOI: 10.1093/AOB/MCQ061
Fluridone: a combination germination stimulant and herbicide for problem fields?
Publisher: Wiley
Date: 13-02-2014
DOI: 10.1002/PS.3721
Abstract: Problem weeds in agriculture, such as Lolium rigidum Gaud., owe some of their success to their large and dormant seed banks, which permit germination throughout a crop-growing season. Dormant weed seed banks could be greatly depleted by application of a chemical that stimulates early-season germination and then kills the young seedlings. Fluridone, a phytoene desaturase-inhibiting herbicide that can also break seed dormancy, was assessed for its efficacy in this regard. The germination of fluridone-treated Lolium rigidum seeds was stimulated on soils with low organic matter, and almost 100% seedling mortality was observed, while the treatment was only moderately effective on a high-organic-matter potting mix. Seedlings from wheat, canola, common bean and chickpea seeds sown on fluridone-treated sandy loam were bleached and did not survive, but lupins and field peas grew normally. This proof-of-concept study with fluridone suggests that it may be possible to design safe and effective molecules that act as germination stimulants plus herbicides in a range of crop and soil types: a potentially novel way of utilising herbicides to stimulate seed bank germination and a valuable addition to an integrated weed management system.
Mechanisms of Resistance to Aryloxyphenoxypropionate Herbicides in Two Resistant Biotypes ofAlopecurus myosuroides(blackgrass): Herbicide Metabolism as a Cross-Resistance Mechanism
Publisher: Elsevier BV
Date: 02-1997
Reducing the Risks of Herbicide Resistance: Best Management Practices and Recommendations
Publisher: Cambridge University Press (CUP)
Date: 2012
Abstract: Herbicides are the foundation of weed control in commercial crop-production systems. However, herbicide-resistant (HR) weed populations are evolving rapidly as a natural response to selection pressure imposed by modern agricultural management activities. Mitigating the evolution of herbicide resistance depends on reducing selection through ersification of weed control techniques, minimizing the spread of resistance genes and genotypes via pollen or propagule dispersal, and eliminating additions of weed seed to the soil seedbank. Effective deployment of such a multifaceted approach will require shifting from the current concept of basing weed management on single-year economic thresholds.
RNA ‐Seq transcriptome analysis to identify genes involved in metabolism‐based diclofop resistance in Lolium rigidum
Publisher: Wiley
Date: 08-05-2014
DOI: 10.1111/TPJ.12514
Abstract: Weed control failures due to herbicide resistance are an increasing and worldwide problem that significantly affect crop yields. Metabolism-based herbicide resistance (referred to as metabolic resistance) in weeds is not well characterized at the genetic level. An RNA-Seq transcriptome analysis was used to find candidate genes that conferred metabolic resistance to the herbicide diclofop in a diclofop-resistant population (R) of the major global weed Lolium rigidum. A reference cDNA transcriptome (19 623 contigs) was assembled and assigned putative annotations. Global gene expression was measured using Illumina reads from untreated control, adjuvant-only control, and diclofop treatment of R and susceptible (S). Contigs that showed constitutive expression differences between untreated R and untreated S were selected for further validation analysis, including 11 contigs putatively annotated as cytochrome P450 (CytP450), glutathione transferase (GST), or glucosyltransferase (GT), and 17 additional contigs with annotations related to metabolism or signal transduction. In a forward genetics validation experiment, nine contigs had constitutive up-regulation in R in iduals from a segregating F2 population, including three CytP450, one nitronate monooxygenase (NMO), three GST, and one GT. Principal component analysis using these nine contigs differentiated F2 -R from F2 -S in iduals. In a physiological validation experiment in which 2,4-D pre-treatment induced diclofop protection in S in iduals due to increased metabolism, seven of the nine genetically validated contigs were induced significantly. Four contigs (two CytP450, NMO, and GT) were consistently highly expressed in nine field-evolved metabolic resistant L. rigidum populations. These four contigs were strongly associated with the resistance phenotype and are major candidates for contributing to metabolic diclofop resistance.
Evolution In Action: Glyphosate-Resistant Weeds Threaten World Crops
Publisher: Research Information Ltd.
Date: 12-2008
DOI: 10.1564/19DEC07
Non‐target‐site‐based resistance to ALS‐inhibiting herbicides in six Bromus rigidus populations from Western Australian cropping fields
Publisher: Wiley
Date: 03-2012
DOI: 10.1002/PS.3270
Abstract: Bromus rigidus is a common weed species that has increased in cropping fields owing to limited control options. During a random field survey in Western Australia, six B. rigidus populations that had survived in-crop weed control programmes were collected. The study aimed to determine the resistance profile of these six populations. Based on dose-response studies, all six B. rigidus populations had a low-level resistance to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) while remaining susceptible to herbicides with other modes of action. ALS in vitro activity assays revealed no differences in enzyme sensitivity between susceptible and resistant populations, while the use of malathion (a cytochrome P450 inhibitor) in combination with sulfosulfuron caused the resistant populations to behave like the susceptible population. This study established that these six B. rigidus populations have a low-level resistance to the ALS-inhibiting sulfonylurea herbicides, but are able to be controlled by other herbicide modes of action. The low-level, malathion-reversible resistance, together with a sensitive ALS, strongly suggest that a non-target-site enhanced metabolism is the mechanism of resistance.
ACCase-Inhibiting Herbicide-ResistantAvenaspp. Populations from the Western Australian Grain Belt
Publisher: Cambridge University Press (CUP)
Date: 03-2012
Abstract: Avena spp. are world weeds with many cases of evolved herbicide resistance. In Australia, Avena spp. (wild oat and sterile oat) are a major problem, especially in grain crops. Acetyl-CoA carboxylase (ACCase)–inhibiting herbicides have been used extensively since the late 1970s for Avena spp. control. However, continued reliance on these herbicides has resulted in the evolution of resistant Avena spp. populations. Resistance across many ACCase-inhibiting herbicides was characterized in four Avena spp. populations from the Western Australian grain belt. Dose–response experiments were conducted to determine the level of resistance to the aryloxyphenoxypropionates and cyclohexanediones and to the phenylpyrazoline herbicide pinoxaden. On the basis of resistance index values, all four resistant populations exhibited high-level diclofop resistance but varied in the level of resistance to other ACCase-inhibiting herbicides tested. It is evident that Avena spp. populations from the Western Australian grain belt have evolved resistance to a number of ACCase-inhibiting herbicides.
Eradication of paraquat‐resistant Hordeum glaucum Steud. by prevention of seed production for 3 years
Publisher: Wiley
Date: 06-1992
Recurrent selection with reduced 2,4‐D amine doses results in the rapid evolution of 2,4‐D herbicide resistance in wild radish (Raphanus raphanistrum L.)
Publisher: Wiley
Date: 06-10-2011
DOI: 10.1002/PS.4364
Abstract: When used at effective doses, weed resistance to auxinic herbicides has been slow to evolve when compared with other modes of action. Here we report the evolutionary response of a herbicide-susceptible population of wild radish (Raphanus raphanistrum L.) and confirm that sublethal doses of 2,4-dichlorophenoxyacetic acid (2,4-D) amine can lead to the rapid evolution of 2,4-D resistance and cross-resistance to acetolactate synthase (ALS)-inhibiting herbicides. Following four generations of 2,4-D selection, the progeny of a herbicide-susceptible wild radish population evolved 2,4-D resistance, increasing the LD This study is the first to confirm the rapid evolution of auxinic herbicide resistance through the use of low doses of 2,4-D and serves as a reminder that 2,4-D must always be used at highly effective doses. With the introduction of transgenic auxinic-herbicide-resistant crops in the Americas, there will be a marked increase in auxinic herbicide use and therefore the risk of resistance evolution. Auxinic herbicides should be used only at effective doses and with ersity if resistance is to remain a minimal issue. © 2016 Society of Chemical Industry.
Resistance cost of a cytochrome P450 herbicide metabolism mechanism but not an ACCase target site mutation in a multiple resistant Lolium rigidum population
Publisher: Wiley
Date: 23-06-2005
DOI: 10.1111/J.1469-8137.2005.01465.X
Abstract: Costs of resistance are predicted to reduce plant productivity in herbicide-resistant weeds. Lolium rigidum herbicide-susceptible in iduals (S), in iduals possessing cytochrome P450-based herbicide metabolism (P450) and multiple resistant in iduals possessing a resistant ACCase and enhanced cytochrome P450 metabolism (ACCase/P450) were grown in the absence of mutual plant interaction to estimate plant growth traits. Both P450 and ACCase/P450 resistant phenotypes produced less above-ground biomass than the S phenotype during the vegetative stage. Reduced biomass production in the resistant phenotypes corresponded to a reduced relative growth rate and a lower net assimilation rate and rate of carbon fixation. There were no significant differences between the two resistant phenotypes, suggesting that costs of resistance are associated with P450 metabolism-based resistance. There were no differences in reproductive output among the three phenotypes, indicating that the cost of P450 resistance during vegetative growth is compensated during the production of reproductive structures. The P450-based herbicide metabolism is shown to be associated with physiological resistance costs, which may be manipulated by agronomic management to reduce the evolution of herbicide resistance.
Embodiment, Privacy and Social Robots: May I Remember You?
Publisher: Springer International Publishing
Date: 2017
Glyphosate resistance in Echinochloa colona: phenotypic characterisation and quantification of selection intensity
Publisher: Wiley
Date: 08-04-2015
DOI: 10.1002/PS.4005
Abstract: A population of Echinochloa colona infesting agricultural fields in the northern region of Western Australia evolved glyphosate resistance after 10 years of glyphosate selection. This study identified two phenotypic (susceptible S versus resistant R) lines from within a segregating glyphosate-resistant population. Estimation of survival, growth and reproductive rates of the phenotypes in response to glyphosate selection helped to characterise the level of resistance, fitness and the selection intensity for glyphosate in this species. Estimations of LD(50) (lethal dose) and GR(50) (growth rate) showed an eightfold glyphosate resistance in this population. The resistant index based on the estimation of seed number (SY(n50)) showed a 13-fold resistance. As a result of linear combination of plant survival and fecundity rates, plant fitness values of 0.2 and 0.8 were estimated for the S and R phenotypes when exposed to the low dose of 270 g glyphosate ha(-1). At the recommended dose of 540 g glyphosate ha(-1) , fitness significantly decreased (fivefold) in S plants but remained markedly similar (0.7) in plants of the R phenotype. Thus, the calculated selection intensity (SI) at 540 g glyphosate ha(-1) was much greater (SI = 17) than at 270 g glyphosate ha(-1) (SI = 4). The assessment of plant survival and fecundity in response to glyphosate selection in the S and R phenotypes allowed a greater accuracy in the estimation of population fitness of both phenotypes and thus of glyphosate selection intensity in E. colona. The estimation of seed number or mass of phenotypes under herbicide selection is a true ecological measure of resistance with implications for herbicide resistance evolution.
iHSD mill efficacy on the seeds of Australian cropping system weeds
Publisher: Cambridge University Press (CUP)
Date: 20-11-2018
DOI: 10.1017/WET.2017.95
Abstract: In Australia, widespread evolution of multi-resistant weed populations has driven the development and adoption of harvest weed seed control (HWSC). However, due to incompatibility of commonly used HWSC systems with highly productive conservation cropping systems, better HWSC systems are in demand. This study aimed to evaluate the efficacy of the integrated Harrington Seed Destructor (iHSD) mill on the seeds of Australia’s major crop weeds during wheat chaff processing. Also examined were the impacts of chaff type and moisture content on weed seed destruction efficacy. Initially, the iHSD mill speed of 3,000 rpm was identified as the most effective at destroying rigid ryegrass seeds present in wheat chaff. Subsequent testing determined that the iHSD mill was highly effective ( % seed kill) on all Australian crop weeds examined. Rigid ryegrass seed kill was found to be highest for lupin chaff and lowest in barley, with wheat and canola chaff intermediate. Similarly, wheat chaff moisture reduced rigid ryegrass seed kill when moisture level exceeded 12%. The broad potential of the iHSD mill was evident, in that the reductions in efficacy due to wide-ranging differences in chaff type and moisture content were relatively small (≤10%). The results from these studies confirm the high efficacy and widespread suitability of the iHSD for use in Australian crop production systems. Additionally, as this system allows the conservation of all harvest residues, it is the best HWSC technique for conservation cropping systems.
A novel amino acid substitution Ala‐122‐Tyr in ALS confers high‐level and broad resistance across ALS‐inhibiting herbicides
Publisher: Wiley
Date: 19-03-2012
DOI: 10.1002/PS.3278
Abstract: Wild radish, a problem weed worldwide, is a severe dicotyledonous weed in crops. In Australia, sustained reliance on ALS-inhibiting herbicides to control this species has led to the evolution of many resistant populations endowed by any of several ALS mutations. The molecular basis of ALS-inhibiting herbicide resistance in a novel resistant population was studied. ALS gene sequencing revealed a previously unreported substitution of Tyr for Ala at amino acid position 122 in resistant in iduals of a wild radish population (WARR30). A purified subpopulation in idually homozygous for the Ala-122-Tyr mutation was generated and characterised in terms of its response to the different chemical classes of ALS-inhibiting herbicides. Whole-plant dose-response studies showed that the purified subpopulation was highly resistant to chlorsulfuron, metosulam and imazamox, with LD₅₀ or GR₅₀ R/S ratio of > 1024, > 512 and > 137 respectively. The resistance to imazypyr was found to be relatively moderate (but still substantial), with LD₅₀ and GR₅₀ R/S ratios of > 16 and > 7.8 respectively. In vitro ALS activity assays showed that Ala-122-Tyr ALS was highly resistant to all tested ALS-inhibiting herbicides. The molecular basis of ALS-inhibiting herbicide resistance in wild radish population WARR30 was identified to be due to an Ala-122-Tyr mutation in the ALS gene. This is the first report of an amino acid substitution at Ala-122 in the plant ALS that confers high-level and broad-spectrum resistance to ALS-inhibiting herbicides, a remarkable contrast to the known mutation Ala-122-Thr endowing resistance to imidazolinone herbicide.
Resistance to AHAS inhibitor herbicides: current understanding
Publisher: Wiley
Date: 20-01-2014
DOI: 10.1002/PS.3710
Abstract: Acetohydroxyacid synthase (AHAS) inhibitor herbicides currently comprise the largest site-of-action group (with 54 active ingredients across five chemical groups) and have been widely used in world agriculture since they were first introduced in 1982. Resistance evolution in weeds to AHAS inhibitors has been rapid and identified in populations of many weed species. Often, evolved resistance is associated with point mutations in the target AHAS gene however non-target-site enhanced herbicide metabolism occurs as well. Many AHAS gene resistance mutations can occur and be rapidly enriched owing to a high initial resistance gene frequency, simple and dominant genetic inheritance and lack of major fitness cost of the resistance alleles. Major advances in the elucidation of the crystal structure of the AHAS (Arabidopsis thaliana) catalytic subunit in complex with various AHAS inhibitor herbicides have greatly improved current understanding of the detailed molecular interactions between AHAS, cofactors and herbicides. Compared with target-site resistance, non-target-site resistance to AHAS inhibitor herbicides is less studied and hence less understood. In a few well-studied cases, non-target-site resistance is due to enhanced rates of herbicide metabolism (metabolic resistance), mimicking that occurring in tolerant crop species and often involving cytochrome P450 monooxygenases. However, the specific herbicide-metabolising, resistance-endowing genes are yet to be identified in resistant weed species. The current state of mechanistic understanding of AHAS inhibitor herbicide resistance is reviewed, and outstanding research issues are outlined.
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