ORCID Profile
0000-0002-7588-124X
Current Organisation
University of Adelaide
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Publisher: Springer Science and Business Media LLC
Date: 12-2003
DOI: 10.1023/B:TRAG.0000005147.04075.62
Abstract: A common concern expressed about the commercial release of transgenic canola into cropping systems is the risks of unwanted gene flow between varieties. Experimental data is emerging that answers some of the theoretical questions that have been posed when considering gene flow on a landscape scale. This study developed models that utilise some of this published data in an attempt to quantify the spread of transgenes in a commercial farming system. The models, which included bootstrapping the empirical data and three mathematical simulations, were compared with each other and the published data. One of the mathematical models estimated average resistance frequency by imposing a Poisson distribution around the published mean value for a single transgenic field surrounded by conventional canola fields and the other two were derived from the theory that pollen flow decreased with distance in the form of a log decay curve. The predictions of all models suggested that the average frequency of resistance occurring from pollen flow in neighbouring canola fields, even when multiple transgenic fields are adjacent to the conventional fields, are likely to be below the current internationally accepted thresholds for contamination.
Publisher: Elsevier BV
Date: 02-1996
Publisher: Springer Science and Business Media LLC
Date: 13-07-2007
DOI: 10.1007/S00122-007-0576-3
Abstract: Resistance to ALS-inhibiting herbicides in Lactuca serriola first appeared in the northern Yorke Peninsula in South Australia in 1994, with resistance soon observed at a number of additional sites. The rapid appearance of resistance at many sites could be attributed to a number of independent selection events or to movement of resistant seed from the original field. ISSRs were used to genotype plants collected in 1999 and 2004 from roadsides or fields in an attempt to determine the importance of these two factors in the spread of herbicide resistance in L. serriola. In 1999 and 2004, chlorsulfuron-resistant L. serriola plants were found in both fields and roadsides with resistant plants being more frequent in fields than roadsides and more frequent in 2004 than in 1999. Genetic relationships generated using UPGMA analysis indicated the presence of more than one genotype within the herbicide resistant populations s led for both years and suggested independent selection as well as movement of resistant seed had occurred. DNA extracted from s les collected in 1999 was used to sequence a highly conserved region of the ALS gene that coded for a single amino acid modification within the gene. Four different mutations were identified within the resistant s les and these mutations tended to cluster on a geographical basis. Together these data provide evidence for both multiple independent evolutionary events and for the potential movement of in idual genotypes as far as 43 km in the region.
Publisher: Springer Science and Business Media LLC
Date: 08-03-2019
DOI: 10.1007/S00425-019-03124-3
Abstract: Glufosinate is primarily toxic to plants due to a massive light-dependent generation of reactive oxygen species rather than ammonia accumulation or carbon assimilation inhibition. Glutamine synthetase (GS) plays a key role in plant nitrogen metabolism and photorespiration. Glufosinate (C
Publisher: Wiley
Date: 03-2017
DOI: 10.1111/WBM.12111
Publisher: Wiley
Date: 1987
DOI: 10.1111/J.1365-3040.1987.TB02084.X
Abstract: Stacking of thylakoid membranes in vitro was assessed using electron microscopy. Grana stacks of spinach thylakoids formed when 5 mol m
Publisher: Cambridge University Press (CUP)
Date: 10-2006
DOI: 10.1614/WS-06-027R.1
Abstract: Trifluralin is widely used for control of rigid ryegrass in no-till grain crops in southern Australia. Trifluralin must be incorporated into soil to be effective. Several field studies were conducted to evaluate the effect of different tillage systems on vertical seed distribution and efficacy and rate of loss of bioavailable trifluralin. Experiments were conducted during the growing seasons of 2004 and 2005 at two sites in South Australia: on the Roseworthy C us farm of the University of Adelaide and near Minlaton on the Yorke Peninsula. The tillage systems at the Roseworthy C us were minimum tillage (MinTill) and no-till using narrow points, whereas four direct-drill-seeding systems were used at Minlaton. Plastic beads were spread on the soil surface to simulate weed seeds. MinTill sowing buried more plastic beads than no-till, indicating that greater soil disturbance was caused by the MinTill system. Trifluralin efficacy was lower under no-till as compared to MinTill. A bioassay, based on response of oat roots, was used to quantify the concentrations of bioavailable trifluralin under different tillage systems. In both years at the Roseworthy C us, loss of bioavailable trifluralin was greater under no-till than under MinTill however, the rate of loss under both systems was much faster in 2004 than in 2005. In 2004, bioavailable trifluralin at 12 d after sowing under MinTill and no-till was 55 and 33% of the initial concentration, respectively. In 2005, bioavailable trifluralin remaining at 23 d after sowing was 86% under MinTill and 54% under no-till. At Minlaton in both years, bioavailable trifluralin was greater under tillage systems that provided the highest level of soil disturbance. These results demonstrate that reduced bioavailability of trifluralin occurs in no-till seeding systems, which could result in reduced weed control.
Publisher: Cambridge University Press (CUP)
Date: 09-12-2020
DOI: 10.1017/WET.2020.134
Abstract: In southern Australia, annual sowthistle and prickly lettuce have become more prevalent following the adoption of reduced tillage cropping systems. They are especially problematic in lentil and other pulse crops, which are weakly competitive and have few herbicide options available for POST control of broadleaf weeds. This study aimed to evaluate the influence of management in a previous cereal crop on weed densities in a subsequent crop. At two field sites, crop seeding density and POST herbicide treatments (a conventional choice that included metsulfuron-methyl and MCPA and a proactive choice that included bromoxynil, picolinafen, and MCPA) were applied to a wheat crop, and weed density was assessed at the beginning of the following season to measure for a legacy effect of the treatments. Study site populations were also screened for herbicide resistance and were found to have high (≥90% survival) ALS inhibitor resistance. Crop competition treatments had no effect on weed populations, and effects of herbicide treatment were significant at only one of the sites. At this site, both herbicide treatments had lower weed densities than the nontreated in the first year, but the legacy effect was only significant for annual sowthistle density in the proactive treatment. At both sites, even where weeds were extremely sparse or completely controlled following herbicide treatment in the first year, moderate densities were observed the following year, indicating that colonization from the seedbank or adjacent areas could be contributing to weed numbers. Weed density assessments and accurate knowledge of the herbicide resistance status of target weeds should guide herbicide selection to maximize control.
Publisher: Elsevier BV
Date: 12-2015
Publisher: Wiley
Date: 30-07-2019
DOI: 10.1002/PS.5087
Abstract: An oriental mustard population (P40) was identified as resistant to diflufenican by screening at the field rate. As diflufenican and picolinafen both target phytoene desaturase (PDS), cross-resistance to picolinafen was suspected. The mechanism of resistance and its inheritance to diflufenican and picolinafen were investigated. At the lethal dose (LD Resistance to diflufenican and picolinafen in the P40 population is likely conferred by Leu-498-Val and Glu-425-Asp mutations in the PDS gene. Inheritance of resistance to these herbicides is managed by a single dominant gene. © 2018 Society of Chemical Industry.
Publisher: CSIRO Publishing
Date: 24-05-2022
DOI: 10.1071/CP21753
Abstract: Context Annual ryegrass (Lolium rigidum) is a major weed of crop production in southern Australia that readily develops resistance to herbicides. Resistance increases both yield losses and control costs associated with this species. Aims This study aimed to gauge the extent and distribution of resistance to herbicides in L. rigidum across south-eastern Australian grain production systems by collecting seed from randomly selected fields. Methods A total of 1441 weed populations were collected through random surveys conducted over 5 years across 13 agricultural regions of four states with these s les then tested for resistance to eight herbicides from six modes of action. Key results Resistance to diclofop-methyl and sulfometuron-methyl was most common, being present in 64% and 63% of populations respectively. Glyphosate resistance was present in 4% of populations collected. Only 15% of populations collected were susceptible to all herbicides tested. Large differences in resistance occurred between the 13 regions surveyed with resistance to diclofop-methyl ranging from 15% to 86% of populations and sulfometuron-methyl from 12% to 96%. Resistance to post-emergent herbicides tended to be higher than pre-emergent herbicides. Multiple resistance was common with 60% of populations collected having resistance to two or more herbicide modes of action. Conclusions There were significant differences in the extent of multiple resistance in L. rigidum populations collected from in idual regions suggesting that the rates of resistance evolution have differed between regions. Implications The high incidence of herbicide resistance in L. rigidum populations randomly collected from south-eastern Australian cropping fields highlights the need for the adoption of additional weed control practices to mitigate the impact of this species on grain production systems.
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.
Publisher: Cambridge University Press (CUP)
Date: 2003
Publisher: Cambridge University Press (CUP)
Date: 11-2006
DOI: 10.1614/WS-06-067.1
Publisher: American Chemical Society (ACS)
Date: 08-10-1991
DOI: 10.1021/BI00104A008
Abstract: The diphenylcarbazide(DPC)/Mn2+ assay [Hsu, B.-D., Lee, J.-Y., & Pan, R.-L. (1987) Biochim. Biophys. Acta 890, 89-96] was used to assess the amount of the high-affinity Mn-binding site in manganese-depleted photosystem II (PS II) membrane fragments from spinach and Scenedesmus obliquus. The assay mechanism at high DPC concentration was shown to involve noncompetitive inhibition of only half of the control level of DPC donation to PS II by micromolar concentrations of Mn at pH 6.5 (i.e., one of two DPC donation sites is inhibited). At low DPC concentration both DPC and Mn2+ donate to PS II additively. Treatment with the carboxyl amino acid modifier 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) inhibited half of the high-affinity Mn-binding site in spinach and Scenedesmus WT PS II membranes and all of the available site in Scenedesmus LF-1 mutant PS II membranes. A similar EDC concentration dependence was observed in all cases. Addition of 2 mM MnCl2 to the 10 mM EDC modification buffer provided complete protection for the Mn-binding site from modification. This protection was specific for Mn2+ six other alent cations were ineffective. We conclude that EDC modifies that half of the high-affinity Mn-binding site that is insensitive to the histidine modifier diethyl pyrocarbonate (DEPC) [Seibert, M., Tamura, N., & Inoue, Y. (1989) Biochim. Biophys. Acta 974, 185-191] and directly affects ligands that bind Mn. The effects of EDC and DEPC that influence the high-affinity site are mutually exclusive and are specific to the lumenal side of the PS II membrane. Removal of the two more loosely bound of the four functional Mn from PS II membranes uncovers that part of the high-affinity site associated with carboxyl but not histidyl residues. We suggest that carboxyl residues on reaction center proteins are associated with half of the high-affinity Mn-binding site in PS II and are involved along with histidine residues in binding Mn functional in the O2-evolving process.
Publisher: Wiley
Date: 15-03-2021
DOI: 10.1002/PS.6333
Abstract: The scale of herbicide resistance within a cropping region can be estimated and monitored using surveys of weed populations. The current approach to herbicide resistance surveys is time‐consuming, logistically challenging and costly. Here we review past and current approaches used in herbicide resistance surveys with the aims of (i) defining effective survey methodologies, (ii) highlighting opportunities for improving efficiencies through the use of new technologies and (iii) identifying the value of repeated region‐wide herbicide resistance surveys. One of the most extensively surveyed areas of the world's cropping regions is the Australian grain production region, with fields randomly surveyed in each of three surveys conducted over the past 15 years. Consequently, recommended methodologies are based on what has been learned from the Australian experience. Traditional seedling‐based herbicide screening assays remain the most reliable and widely applicable method for characterizing resistance in weed populations. The use of satellite or aerial imagery to plan collections and image analysis to rapidly quantify screening results could complement traditional resistance assays by increasing survey efficiency and s ling accuracy. Global management of herbicide‐resistant weeds would benefit from repeated and standardized surveys that track herbicide resistance evolution within and across cropping regions. © 2021 Society of Chemical Industry.
Publisher: American Chemical Society (ACS)
Date: 10-1991
DOI: 10.1021/BI00104A009
Abstract: The "high-affinity Mn-binding site" in Mn-depleted photosystem II (PS II) membrane fragments isolated from Scenedesmus obliquus was examined by using the diphenylcarbazide (DPC)/Mn2+ non-competitive inhibition assay [Preston, C., & Seibert, M. (1991) Biochemistry (preceding paper in this issue)]. Different proteases were used to degrade lumenal surface protein segments from these PS II membranes, and a total of four independent high-affinity Mn-binding sites (ligands) were identified. Carboxypeptidase A, subtilisin, and Staphylococcus aureus V8 protease each degrade one of two high-affinity Mn-binding sites sensitive to the histidine chemical modifier diethyl pyrocarbonate (DEPC). However, sequential treatment experiments indicate that subtilisin degrades a DEPC-sensitive Mn-binding site that is different from the one degraded by the other two proteases. Trypsin also was found to degrade one of the DEPC-sensitive Mn-binding sites (that degraded by carboxypeptidase A and V8 protease). In addition, trypsin degrades one of two 1-ethyl-3-[(3-dimethylamino)propyl]carbodiimide (EDC) sensitive Mn-binding sites, but only in the absence of the 30-kDa extrinsic protein. Thus, the 30-kDa extrinsic protein associated with O2 evolution appears to protect the EDC-sensitive binding site from trypsin degradation. No protease has yet been identified that will degrade the trypsin-insensitive EDC-sensitive Mn-binding site. Under the conditions of the assay (high DPC concentration), more than three Mn per reaction center were found bound to the membrane with a KM of about 0.4 microM, as determined by direct metal analysis. This is consistent with the idea that each of the four high-affinity sites binds (or provides a ligand for) one of four Mn.(ABSTRACT TRUNCATED AT 250 WORDS)
Publisher: Wiley
Date: 23-08-2012
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.
Publisher: Cambridge University Press (CUP)
Date: 09-2012
Abstract: Glyphosate is widely used for weed control in the grape growing industry in southern Australia. The intensive use of glyphosate in this industry has resulted in the evolution of glyphosate resistance in rigid ryegrass. Two populations of rigid ryegrass from vineyards, SLR80 and SLR88, had 6- to 11-fold resistance to glyphosate in dose-response studies. These resistance levels were higher than two previously well-characterized glyphosate-resistant populations of rigid ryegrass (SLR77 and NLR70), containing a modified target site or reduced translocation, respectively. Populations SLR80 and SLR88 accumulated less glyphosate, 12 and 17% of absorbed glyphosate, in the shoot in the resistant populations compared with 26% in the susceptible population. In addition, a mutation within the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) where Pro 106 had been substituted by either serine or threonine was identified. These two populations are more highly resistant to glyphosate as a consequence of expressing two different resistance mechanisms concurrently.
Publisher: Cambridge University Press (CUP)
Date: 06-2014
Abstract: In Australia, most wheat is sown in a no-till system without prior cultivation where herbicides are applied prior to sowing and incorporated by the planter. Trifluralin has been the most widely used PRE herbicide to control rigid ryegrass. The objective of this research was to determine crop safety and efficacy of alternative mechanism of action PRE herbicides for rigid ryegrass control in no-till wheat production. Pyroxasulfone achieved 98% control with PRE applications. The alternative PRE herbicides tested alone and in mixtures occasionally resulted in a significant reduction in wheat emergence but not crop yield. Trifluralin treatments failed at sites having trifluralin-resistant rigid ryegrass. Pyroxasulfone and prosulfocarb plus S -metolachlor were effective for control of rigid ryegrass across all trials with control ranging from 64 to 94%. This research demonstrated that PRE applications of herbicides other than trifluralin such as pyroxasulfone and prosulfocarb plus S -metolachlor can be safely and effectively used to control rigid ryegrass in no-till wheat.
Publisher: Informa UK Limited
Date: 02-2008
DOI: 10.1080/03601230701794968
Abstract: The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled conditions. Hydrolysis, where it occurred, and photodegradation both followed first-order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7 however, slow hydrolysis occurred at pH 9. Estimated half-lives for the three herbicides in solution in the dark were 6.5, 9.2 and 9.6 months for imazaquin, imazethapyr and imazapyr, respectively. Degradation of the herbicides in the light was considerably more rapid than in the dark with half lives for the three herbicides of 1.8, 9.8 and 9.1 days for imazaquin, imazethapyr and imazapyr, respectively. The presence of humic acids in the solution reduced the rate of photodegradation for all three herbicides, with higher concentrations of humic acids generally having greater effect. Photodegradation of imazethapyr was the least sensitive to humic acids. The enantioselectivity of photodegradation was investigated using imazaquin, with photodegradation occurring at the same rate for both enantiomers. Abiotic degradation of imidazolinone herbicides on the soil surface only occurred in the presence of light. The rate of degradation for all herbicides was slower than in solution, with half-lives of 15.3, 24.6 and 30.9 days for imazaquin, imazethapyr and imazapyr, respectively. Abiotic degradation of these herbicides is likely to be slow in the environment and is only likely to occur in clear water or on the soil surface.
Publisher: Cambridge University Press (CUP)
Date: 03-2007
DOI: 10.1614/WT-06-016.1
Abstract: Experiments were conducted at Minlaton on the Yorke Peninsula of South Australia in 2004 and 2005 to study the effect of four different seeding systems and dinitroaniline herbicides on the seedling emergence and growth of rigid ryegrass in wheat. The seeding systems were low soil-disturbance discs (DayBreak and K-Hart) and high soil-disturbance tines (narrow point and Ribbon seeder) and the herbicides were oryzalin, pendimethalin, and trifluralin at rate of 0.72 kg ai/ha. The total seedling emergence of rigid ryegrass was higher in nontreated plots planted with the tines compared with the discs. In general, oryzalin was the least-effective herbicide in controlling emergence of rigid ryegrass. All herbicides were more effective in reducing the number of plants, spikes, dry matter, and seed production of rigid ryegrass in combination with tines than with discs. However, in the absence of herbicides, plant and spike numbers, plant dry weight, and seed production of rigid ryegrass were significantly lower where discs were used to sow, rather than tines. In the absence of herbicide, rigid ryegrass was less competitive with wheat under the disc-sown systems. The response of grain yield to herbicides was greater under the tine-sown systems than the disc-sown systems.
Publisher: Elsevier
Date: 2014
Publisher: Cambridge University Press (CUP)
Date: 10-2006
DOI: 10.1614/WS-06-047R.1
Abstract: Annual sowthistle has become more abundant under no-till systems in southern Australia. Increased knowledge of germination biology of annual sowthistle would facilitate development of effective weed control programs. The effects of environmental factors on germination and emergence of annual sowthistle seeds were examined in laboratory and field experiments. Seeds of annual sowthistle were able to germinate over a broad range of temperatures (25/15, 20/12, and 15/9 C day/night temperatures). Seed germination was favored by light however, some germination occurred in the dark as well. Greater than 90% of seeds germinated at a low level of salinity (40 mM NaCl), and some seeds germinated even at 160 mM NaCl (7.5%). Germination decreased from 95% to 11% as osmotic potential increased from 0 to −0.6 MPa and was completely inhibited at osmotic potential greater than −0.6 MPa. Seed germination was greater than 90% over a pH range of 5 to 8, but declined to 77% at pH 10. Seedling emergence was the greatest (77%) for seeds present on the soil surface but declined with depth, and no seedlings emerged from a soil depth of 5 cm. In another experiment in which seeds were after-ripened at different depths in a field, seed decay was greater on the soil surface than at 2 or 5 cm depth. At the end of the growing season, there was a much greater persistence of buried seed (32 to 42%) than seeds present on the soil surface (8%). Greater persistence of buried seed could be due to dormancy enforced by dark in this species.
Publisher: Springer Science and Business Media LLC
Date: 06-1988
DOI: 10.1007/BF00028838
Publisher: Cambridge University Press (CUP)
Date: 05-2006
Publisher: Elsevier BV
Date: 10-2004
Publisher: Cambridge University Press (CUP)
Date: 10-2006
DOI: 10.1614/WS-06-053R.1
Abstract: Germination of African mustard seeds collected from southern Australia was not influenced by light conditions at the optimum temperature of 20/12 C. However, seed germination was inhibited by light at the lower temperature (15/9 C). Presence of light increased the sensitivity of seeds to low temperature, as well as salt and osmotic stress. In dark conditions, seed germination was relatively unaffected at a low level of salinity (80 mM NaCl) but decreased even at 10 mM NaCl in light/dark conditions. In the dark, seed germination was unaffected up to an osmotic potential of −0.6 MPa but declined thereafter. Seeds of African mustard germinated over a broad range of pH from 4 to 10. Seed germination was stimulated by potassium nitrate (from 0.005 to 0.04 M) and gibberellic acid (0.001 M). Seedling emergence of African mustard was the greatest (51%) for seeds buried at 1 cm but no seedlings emerged from seeds placed at a depth of 5 cm. At the end of the growing season, seed decay (77 to 87%) and dormant (12 to 18%) components were similar among different seed burial depths. Information gained in this study will be important in developing a better understanding of the requirements for African mustard germination and emergence.
Publisher: Springer Science and Business Media LLC
Date: 03-2001
Publisher: Wiley
Date: 11-2017
Publisher: Cambridge University Press (CUP)
Date: 30-10-2018
DOI: 10.1017/WSC.2017.67
Abstract: Populations of rigid ryegrass suspected of resistance to trifluralin due to control failures exhibited varying levels of susceptibility to trifluralin, with 15 out of 17 populations deemed resistant ( % plant survival). Detailed dose–response studies were conducted on one highly resistant field-evolved population (SLR74), one known multiply resistant population (SLR31), and one susceptible population (VLR1). On the basis of the dose required to kill 50% of treated plants (LD 50 ), SLR74 had 15-fold greater resistance than VLR1, whereas, the multiply resistant SLR31 had 10-fold greater resistance than VLR1. Similarly, on the basis of dose required to reduce shoot biomass by 50% (GR 50 ), SLR74 had 17-fold greater resistance than VLR1, and SLR31 had 8-fold greater resistance than VLR1. Sequencing of the α-tubulin gene from resistant plants of different populations confirmed the presence of a previously known goosegrass mutation causing an amino acid substitution at position 239 from threonine to isoleucine in resistant population SLR74. This mutation was also found in 4 out of 5 in iduals in another highly resistant population TR2 and in 3 out of 5 in iduals of TR4. An amino acid substitution from valine to phenylalanine at position 202 was also observed in TR4 (3 out of 5 plants) and TR2 (1 out of 5 plants). There was no target-site mutation identified in SLR31. This study documents the first known case of field-evolved target-site resistance to dinitroaniline herbicides in a population of rigid ryegrass.
Publisher: Cambridge University Press (CUP)
Date: 11-2006
DOI: 10.1614/WS-06-092.1
Publisher: Springer Science and Business Media LLC
Date: 06-1995
DOI: 10.1007/BF00203645
Publisher: Wiley
Date: 26-02-2018
DOI: 10.1002/PS.4858
Abstract: An oriental mustard population (P3) collected near Quambatook, Victoria was identified as being resistant to diflufenican by screening with the field rate (200 g a.i. ha Dose-response experiments confirmed that population P3 was 140-fold more resistant to diflufenican than susceptible populations, as determined by the comparison of 50% lethal (LD Resistance to diflufenican in oriental mustard is conferred by the Leu-526-Val mutation in the PDS gene. Inheritance of resistance is managed by a single gene with high levels of dominance. © 2018 Society of Chemical Industry.
Publisher: Wiley
Date: 13-12-2008
DOI: 10.1002/PS.1508
Abstract: Glyphosate-resistant cotton varieties are an important tool for weed control in Australian cotton production systems. To increase the sustainability of this technology and to minimise the likelihood of resistance evolving through its use, weed scientists, together with herbicide regulators, industry representatives and the technology owners, have developed a framework that guides the use of the technology. Central to this framework is a crop management plan (CMP) and grower accreditation course. A simulation model that takes into account the characteristics of the weed species, initial gene frequencies and any associated fitness penalties was developed to ensure that the CMP was sufficiently robust to minimise resistance risks. The simulations showed that, when a combination of weed control options was employed in addition to glyphosate, resistance did not evolve over the 30 year period of the simulation. These simulations underline the importance of maintaining an integrated system for weed management to prevent the evolution of glyphosate resistance, prolonging the use of glyphosate-resistant cotton.
Publisher: Elsevier BV
Date: 10-2002
Publisher: Wiley
Date: 30-09-2014
DOI: 10.1111/WRE.12050
Publisher: American Chemical Society (ACS)
Date: 09-1998
DOI: 10.1021/BI980359O
Publisher: Cambridge University Press (CUP)
Date: 11-2006
DOI: 10.1614/WS-06-087R.1
Publisher: Wiley
Date: 08-09-2006
Publisher: Cambridge University Press (CUP)
Date: 09-2015
Abstract: Two field experiments were conducted during 2012 and 2013 at Roseworthy, South Australia to identify effective herbicide options for the management of clethodim-resistant rigid ryegrass in faba bean. Dose–response experiments confirmed resistance in both field populations (B3, 2012 and E2, 2013) to clethodim and butroxydim. Sequencing of the target site of acetyl coenzyme A carboxylase gene in both populations identified an aspartate-2078-glycine mutation. Although resistance of B3 and E2 populations to clethodim was similar (16.5- and 21.4-fold more resistant than the susceptible control SLR4), the B3 population was much more resistant to butroxydim (7.13-fold) than E2 (2.24-fold). Addition of butroxydim to clethodim reduced rigid ryegrass plant density 60 to 80% and seed production 71 to 88% compared with the standard grower practice of simazine PPI plus clethodim POST. Clethodim + butroxydim combination had the highest grain yield of faba bean (980 to 2,400 kg ha −1 ). Although propyzamide and pyroxasulfone plus triallate PPI provided the next highest levels of rigid ryegrass control ( 60%), these treatments were more variable and unable to reduce seed production (6,354 to 13,570 seeds m −2 ) to levels acceptable for continuous cropping systems.
Publisher: Cambridge University Press (CUP)
Date: 11-2006
Publisher: Wiley
Date: 1987
Publisher: Elsevier BV
Date: 02-1990
DOI: 10.1016/0005-2728(90)90017-X
Abstract: We have measured the decay of chlorophyll a fluorescence at 4 degrees C under anaerobic conditions in stabilized photosystem II reaction center complex isolated from spinach, using multifrequency (2-400 MHz) cross-correlation phase fluorometry. Examination of our data shows that although the fluorescence decay of open reaction centers (i.e., when both the electron donor P-680 and the electron acceptor pheophytin are capable of engaging in charge separation) can be analyzed as a multiexponential decay, another representation of the data is obtained when the decay is analyzed using a continuous distribution of lifetimes. Our results on the open reaction center differ from the two lifetime components of 25 ps and 35 ns published by Mimuro et al. (Biochim. Biophys. Acta 933 (1988) 478-486) for the D1-D2-cytochrome b-559 complex, obtained for F682 at 4 degrees C by a time-resolved photon-counting spectrofluorometer. When the reaction centers are closed by pretreatment with sodium dithionite and methyl viologen followed by exposure to laser excitation, conditions known to result in accumulation of reduced pheophytin, a dramatic decrease in the contribution of the slow lifetime component(s) is observed. These results suggest that the slow distribution lifetime component(s) in the 5-20 ns range originate(s) in the back reaction of the charge separated state. On the other hand, the fast lifetime component(s) in the picosecond range may be only partially related to the charge separation, since no dramatic change is observed upon closure of the reaction center. Perhaps, this component is related, in part, to the excitation energy migration among the various chromophores in the reaction center preparations.
Publisher: Elsevier BV
Date: 12-1998
Publisher: Elsevier BV
Date: 11-2001
Publisher: Wiley
Date: 02-05-2017
DOI: 10.1002/PS.4573
Abstract: Five glyphosate-resistant populations of Chloris truncata originally collected from New South Wales were compared with one susceptible (S) population from South Australia to confirm glyphosate resistance and elucidate possible mechanisms of resistance. Based on the amounts of glyphosate required to kill 50% of treated plants (LD This study has identified EPSPS gene lification contributing to glyphosate resistance in C. truncata. In addition, a Glu-91-Ala mutation within EPSPS was identified that may contribute to glyphosate resistance in this species. © 2017 Society of Chemical Industry.
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 03-2007
Publisher: Springer Science and Business Media LLC
Date: 12-2003
DOI: 10.1038/NBT1203-1429
Publisher: Oxford University Press (OUP)
Date: 1994
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/AR07436
Abstract: Canola is an important crop in southern Australia, where it is used as part of the crop rotation to manage cereal diseases, improve wheat yields, and assist in integrated weed management programs. The potential release of herbicide-tolerant transgenic cultivars into Australia has raised concerns that volunteer canola may itself become an uncontrollable weed. This study examined the persistence of the canola seedbank in farmer-managed fields in 3 geographical areas of the South Australian cropping region for up to 3.5 years after the last canola crop was grown. In total, 66 fields from minimum- and no-tillage farms were s led for number of canola seed/m2 and the percentage of those that germinated. ANOVA analysis indicated that time since the last harvest and cultivation method were both significant factors affecting the number of seed/m2 present. Neither time since harvest nor cultivation method was significant for number of germinated canola seeds, although time since harvest approached significance at the 5% level. This demonstrates that the canola seedbank and the number of volunteers decline rapidly in managed cropping systems in southern Australia. Therefore, it is unlikely that herbicide-tolerant canola will become a major weed if volunteers are managed carefully.
Publisher: Wiley
Date: 14-02-2018
DOI: 10.1002/PS.4845
Abstract: Two oriental mustard populations (P2 and P13) collected from Port Broughton, South Australia were identified as resistant to 2,4-D. The level of resistance, mechanism and the mode of inheritance for 2,4-D resistance in these populations were investigated. Populations P2 and P13 were confirmed to be resistant to 2,4-D at the field rate (600 g a.e. ha Resistance to 2,4-D in oriental mustard is likely due to reduced translocation of 2,4-D out of the treated leaf. Inheritance of 2,4-D resistance is conferred by a single gene with a high level of dominance. © 2017 Society of Chemical Industry.
Publisher: Elsevier BV
Date: 06-2009
DOI: 10.1016/J.CHROMA.2009.04.080
Abstract: Extraction and quantification of herbicide residues from soil are important in understanding the behaviour of persistent herbicides. This research investigated extraction and clean-up methods for imidazolinone herbicides from soil and soil amended with organic material. A series of solvent mixes, pH conditions and sorbents was tested. Across three imidazolinone herbicides: imazapyr, imazethapyr and imazaquin, 0.5M NaOH extraction gave greater than 90% recovery from soil s les however, 0.5M NaOH:MeOH (80:20) resulted in higher recovery for imazaquin, but not for the other two herbicides. Of the sorbents tested, the use of chromatographic mode sequencing using C(18) and SCX sorbents provided consistent high (>85%) recovery of all three herbicides from soil and separation of the herbicides from other soil components by high performance liquid chromatography (HPLC). These two methods will allow high recovery of these imidazolinone herbicides from soil and have the ability to detect these herbicides without interference from other soil components.
Publisher: Cambridge University Press (CUP)
Date: 06-2016
Abstract: A field study was undertaken to investigate the influence of different management strategies on rigid ryegrass plant density and seedbank dynamics over 4 yr. Even though weed seedbank declined by 86% after oaten hay in year 1, the residual seedbank enabled rigid ryegrass to reinfest field peas the next year, and the population rebounded sharply when weed control relied solely on PPI trifluralin. However, use of POST clethodim followed by crop-topping for seed-set prevention of rigid ryegrass in field pea was highly effective and caused a further decline in the weed seedbank. Integration of effective management tactics over 3 yr significantly reduced rigid ryegrass weed and spike density (90 and 81%) in the final year of the 4-yr cropping sequence. Use of oaten hay in year 1, followed by effective weed control in field pea and wheat crops, depleted the high initial seedbank (4,820 seeds m −2 ) to moderate levels ( 200 seeds m −2 ) within 3 yr. Effective weed-management treatments depleted the rigid ryegrass seedbank, reduced in-crop weed infestation, and returned higher grain yields and profitability. The results of this study clearly show that large rigid ryegrass populations can be managed effectively without reducing crop productivity and profitability provided multiyear weed-management programs are implemented effectively.
Publisher: Cambridge University Press (CUP)
Date: 03-2014
Abstract: Populations of rigid ryegrass with resistance to glyphosate have started to become a problem on fence lines of cropping fields of southern Australian farms. Seed of rigid ryegrass plants that survived glyphosate application were collected from two fence line locations in Clare, South Australia. Dose–response experiments confirmed resistance of these fence line populations to glyphosate. Both populations required 9- to 15-fold higher glyphosate dose to achieve 50% mortality in comparison to a standard susceptible population. The mechanism of resistance in these populations was investigated. Sequencing a conserved region of the gene encoding 5-enolpyruvyl-shikimate-3-phosphate synthase identified no differences between the resistant and susceptible populations. Absorption of glyphosate into leaves of the resistant populations was not different from the susceptible population. However, the resistant plants retained significantly more herbicide in the treated leaf blades than did the susceptible plants. Conversely, susceptible plants translocated significantly more herbicide to the leaf sheaths and untreated leaves than the resistant plants. The differences in translocation pattern for glyphosate between the resistant and susceptible populations of rigid ryegrass suggest resistance is associated with altered translocation of glyphosate in the fence line populations.
Publisher: Proceedings of the National Academy of Sciences
Date: 25-02-2022
Abstract: Synthetic auxin herbicides intersect basic plant developmental biology and applied weed management. We investigated resistance to 2,4-D in the Australian weed Sisymbrium orientale (Indian hedge mustard). We identified a mechanism involving an in-frame 27-bp deletion in the degron tail of auxin coreceptor IAA2, one member of the gene family of Aux/IAA auxin co-receptors. We show that this deletion in IAA2 is a gain-of-function mutation that confers synthetic auxin resistance. This field-evolved mechanism of resistance to synthetic auxin herbicides confirms previous biochemical studies showing the role of the Aux/IAA degron tail in regulating Aux/IAA protein degradation upon auxin perception. The deletion mutation could be generated in crops using gene-editing approaches for cross-resistance to multiple synthetic auxin herbicides.
Publisher: CRC Press
Date: 02-2018
Publisher: CRC Press
Date: 12-07-2017
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1614/WS-05-135R.1
Abstract: Differences in periodicity and depth of weed seedling recruitment due to agronomic management practices, such as reduced tillage, have implications for weed competitive ability and management strategies. Periodicity and depth of seedling recruitment of 10 different weed species was measured in the field in 2004 and 2005. The seedling recruitment of rigid ryegrass, threehorn bedstraw, and wild radish seedlings was higher under minimum tillage than under no-till scenarios. In contrast, the seedling recruitment of Oriental mustard, annual sowthistle, squirreltail fescue, little mallow, and turnipweed was higher under the no-till system. The seedling recruitment of wild oat and African mustard was not influenced by the tillage system. The mean seedling recruitment depth of wild oat, rigid ryegrass, threehorn bedstraw, wild radish, and turnipweed was greater under minimum tillage than under the no-till system. These weeds are able to emerge from deeper in the soil profile. In contrast, the seedling recruitment depth under minimum-tillage and no-till systems was similar for African mustard, Oriental mustard, annual sowthistle, little mallow, and squirreltail fescue. These are all small-seeded species, which failed to emerge from deeper depths under either tillage system. In addition, all of these species except African mustard showed higher total seedling recruitment under the no-till system. Results of this study will facilitate weed-control timing decisions and provide validation data for weed seedling recruitment models.
Publisher: Oxford University Press (OUP)
Date: 10-1992
DOI: 10.1104/PP.100.2.630
Publisher: Wiley
Date: 2000
DOI: 10.1002/(SICI)1526-4998(200005)56:5<441::AID-PS159>3.0.CO;2-L
Publisher: Cambridge University Press (CUP)
Date: 06-2016
Abstract: Smooth barley is an annual weed species that is infesting crops and pastures in South Australia. Complicating control options is the presence of herbicide-resistant biotypes. A field trial was conducted to identify alternative herbicides for the management of acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicide-resistant smooth barley in field pea. Preplant (PP) soil applications of pyroxasulfone prosulfocarb plus S -metolachlor dimethenamid-P propyzamide trifluralin alone or with triallate or with diuron or imazamox applied POST were evaluated for their effectiveness and crop safety. Propyzamide, pyroxasulfone, or imazamox applied POST provided a high level of smooth barley control, did not cause any crop injury, and increased field pea grain or forage yield compared with the nontreated. Furthermore, propyzamide or pyroxasulfone reduced panicle density and seed production in smooth barley, whereas the effectiveness of POST imazamox varied over the two seasons. Dimethenamid-P reduced the impact of smooth barley on field pea yield, but cause stunting, and was less effective than propyzamide, pyroxasulfone, and imazamox in reducing smooth barley seed production. Negative relationship between field pea yield and smooth barley panicle density indicated that smooth barley is highly competitive in field pea crops and can cause large yield losses. The results of this investigation suggest that propyzamide or pyroxasulfone applied PP and imazamox applied POST could be used effectively in the field for the management of ACCase-inhibiting herbicide-resistant smooth barley in South Australia.
Publisher: Cambridge University Press (CUP)
Date: 08-2009
DOI: 10.1614/WS-08-181.1
Abstract: Glyphosate resistance was first discovered in populations of rigid ryegrass in Australia in 1996. Since then, glyphosate resistance has been detected in additional populations of rigid ryegrass and Italian ryegrass in several other countries. Glyphosate-resistant rigid ryegrass and Italian ryegrass have been selected in situations where there is an overreliance on glyphosate to the exclusion of other weed control tactics. Two major mechanisms of glyphosate resistance have been discovered in these two species: a change in the pattern of glyphosate translocation such that glyphosate accumulates in the leaf tips of resistant plants instead of in the shoot meristem and amino acid substitutions at Pro 106 within the target site, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). There are also populations with both mechanisms. In the case of glyphosate resistance, the target site mutations tend to provide a lower level of resistance than does the altered translocation mechanism. Each of these resistance mechanisms is inherited as a single gene trait that is largely dominant. As these ryegrass species are obligate outcrossers, this ensures resistance alleles can move in both pollen and seed. Some glyphosate-resistant rigid ryegrass populations appear to have a significant fitness penalty associated with the resistance allele. Field surveys show that strategies vary in their ability to reduce the frequency of glyphosate resistance in populations and weed population size, with integrated strategies—including alternative weed management and controlling seed set of surviving plants—the most effective.
Publisher: American Chemical Society (ACS)
Date: 26-01-2012
DOI: 10.1021/JF203472S
Abstract: Lolium spp., ryegrass, variants from Australia, Brazil, Chile, and Italy showing differing levels of glyphosate resistance were examined by (31)P NMR. Extents of glyphosate (i) resistance (LD(50)), (ii) inhibition of 5-enopyruvyl-shikimate-3-phosphate synthase (EPSPS) activity (IC(50)), and (iii) translocation were quantified for glyphosate-resistant (GR) and glyphosate-sensitive (GS) Lolium multiflorum Lam. variants from Chile and Brazil. For comparison, LD(50) and IC(50) data for Lolium rigidum Gaudin variants from Italy were also analyzed. All variants showed similar cellular uptake of glyphosate by (31)P NMR. All GR variants showed glyphosate sequestration within the cell vacuole, whereas there was minimal or no vacuole sequestration in the GS variants. The extent of vacuole sequestration correlated qualitatively with the level of resistance. Previous (31)P NMR studies of horseweed ( Conyza canadensis (L.) Cronquist) revealed that glyphosate sequestration imparted glyphosate resistance. Data presented herein suggest that glyphosate vacuolar sequestration is strongly contributing, if not the major contributing, resistance mechanism in ryegrass as well.
Publisher: Wiley
Date: 13-12-2008
DOI: 10.1002/PS.1489
Abstract: Glyphosate-resistant weeds have evolved as a result of the intensive use of glyphosate for weed control. An alteration in the way glyphosate is translocated within the plant has been identified as a mechanism of glyphosate resistance in populations of Lolium rigidum Gaud., L. multiflorum Lam. and Conyza canadensis (L.) Cronq. In these resistant plants, glyphosate becomes concentrated in the leaves rather than being translocating throughout the plant. This type of resistance is inherited as a single dominant or semi-dominant allele. Resistance due to reduced translocation appears to be a common mechanism of resistance in L. rigidum and C. canadensis, probably because it provides a greater level of resistance than other mechanisms. This type of glyphosate resistance also appears to reduce the fitness of plants that carry it. This may influence how glyphosate resistance can be managed.
Publisher: Elsevier BV
Date: 07-2003
Publisher: American Chemical Society
Date: 08-03-2005
Publisher: Cambridge University Press (CUP)
Date: 12-2015
Abstract: Smooth barley has emerged as a problematic weed in cereal crops of South Australia. After the recent reports of herbicide resistance and increase in seed dormancy in smooth barley, it was considered important to determine the herbicide resistance status and seedbank behavior of field populations of this weed species. A field survey was undertaken in the Upper North and Eyre Peninsula regions of South Australia in October 2012. Of the 90 smooth barley populations screened for resistance to quizalofop, 15% exhibited some level of resistance and 85% were susceptible. Resistance to acetolactate synthase (ALS)-inhibiting herbicides was low, with only 3 and 12% of populations classified as developing resistance to imazamox + imazapyr and sulfosulfuron, respectively. No multiple resistance patterns were observed however, two ALS-inhibiting herbicide-resistant populations had sulfonylurea-to-imidazolinone cross-resistance. At the start of the growing season, the majority of smooth barley populations emerged rapidly (median 50% time to emergence [ T 50 ] = 8 d). In contrast, some populations of smooth barley displayed an extremely slow emergence pattern, with T 50 of 20 d. No direct linkage between seed dormancy and herbicide resistance was observed. However, two acetyl coenzyme A carboxylase-inhibiting herbicide-resistant populations were highly dormant and exhibited delayed emergence. The majority of smooth barley populations showed low-level or no seedbank persistence, but a few populations persisted for 1 yr. However, some weed populations had up to 20% seedbank persistence from 1 yr to the next. Overall there was a strong negative relationship between smooth barley seedling emergence and the level of seed persistence ( R 2 = 0.84, P 0.05). This association indicated that greater seed dormancy could be responsible for extended persistence of the seedbank of this weed species. The study provides valuable insights into the general pattern of herbicide resistance and the behavior of the seedbank of smooth barley populations on South Australian farms.
Publisher: Wiley
Date: 11-02-2001
Publisher: Wiley
Date: 02-1997
DOI: 10.1002/(SICI)1096-9063(199702)49:2<105::AID-PS507>3.0.CO;2-3
Publisher: Cambridge University Press (CUP)
Date: 02-2015
Abstract: Since the beginning of agriculture, crops have been exposed to recurrent invasion by weeds that can impose severe reductions in crop quality and yield. There have been continuing efforts to reduce the impacts of weeds on production. More than 40 yr ago, overreliance on herbicide technology to reduce weed infestations resulted in the selection of adaptive traits that enabled weed survival and reproduction under herbicide treatments (Délye et al. 2007 Powles and Yu 2010 Vila-Aiub et al. 2008). As a result, herbicide resistance in & 200 weed species has evolved worldwide (Heap 2013 Powles 2008).
Publisher: Cambridge University Press (CUP)
Date: 02-2009
DOI: 10.1614/WS-08-098.1
Abstract: The inheritance of resistance to the auxinic herbicide dicamba was examined in a kochia population from Nebraska. An inbred, resistant line was developed by selection and selfing over seven generations to ensure any resistance alleles would be homozygous in the parents. An inbred, susceptible line was similarly developed, but without selection. Dose–response experiments with dicamba determined a glyphosate-resistant concentration required to inhibit dry weight accumulation by 50% (GR 50 ) of 45 and 1,331 g ae ha −1 for the susceptible and resistant populations, respectively. F 1 crosses were made between resistant and susceptible inbred in iduals by hand-pollination, and the F 1 plants were selfed to produce F 2 plants. The F 2 population was screened with 280 g ha −1 dicamba, a rate that could discriminate between susceptible and resistant plants. A total of eight F 2 families were screened twice. In the first screen, seven F 2 families segregated in a 3:1 ratio, consistent with a single dominant allele controlling resistance, and in the second screen six F 2 families segregated in a 3:1 ratio. F 2 in iduals were selfed, the F 3 progeny were tested with 280 g ha −1 dicamba, and the genotype of each F 2 parent was determined based on F 3 progeny segregation. F 3 family segregation was consistent with the F 2 parents having a 1:2:1 homozygous-susceptible:heterozygote:homozygous-resistant pattern, confirming that resistance to dicamba in kochia is likely conferred by a single allele with a high degree of dominance.
Publisher: Cambridge University Press (CUP)
Date: 04-05-2020
DOI: 10.1017/WSC.2020.35
Abstract: Annual bluegrass ( Poa annua L.) is a problematic annual weed in established turf where the intensive use of herbicides has resulted in the evolution of herbicide resistance. In 2017, 31 populations of P. annua suspected to be resistant to herbicides commonly used to control this weed in turf were collected from golf courses across southeastern Australia to check the resistance status to different herbicide groups. All populations were found to be resistant to multiple turf herbicides. Dose–response experiments confirmed resistance to propyzamide, simazine, rimsulfuron, foramsulfuron, endothall, and pinoxaden. Levels of resistance to rimsulfuron ( -fold), foramsulfuron ( -fold), endothall ( -fold), and pinoxaden ( .3-fold) compared with the susceptible population were high, but levels of resistance to propyzamide ( -fold) and simazine ( -fold) were lower. Considerable variation in resistance to endothall and pinoxaden was observed among the populations of P. annua . Target-site resistance was confirmed for acetolactate synthase and acetyl-CoA carboxylase inhibitors, but not for photosystem II and microtubule assembly inhibitors. This study documented the extensive resistance to herbicides in P. annua from turf in Australia. Three of the populations investigated exhibited multiple resistance to herbicides from five mechanisms of action. The identification of multiple-resistant P. annua on several golf courses is a serious concern for turf managers.
Publisher: Wiley
Date: 06-11-2007
Publisher: Cambridge University Press (CUP)
Date: 12-05-2020
DOI: 10.1017/WSC.2020.39
Abstract: Glufosinate inhibits glutamine synthetase (GS), a key enzyme for amino acid metabolism and photorespiration. Protoporphyrinogen oxidase (PPO) inhibitors block chlorophyll biosynthesis and cause protoporphyrin accumulation, a highly photodynamic intermediate. Both herbicides ultimately lead to plant death by a massive accumulation of reactive oxygen species (ROS) through different mechanisms. We investigated a potential synergistic effect by the mixture of the two herbicide mechanisms of action (MoAs). The tank mix between a low rate of glufosinate (280 g ai ha −1 ) with an ultra-low dose of saflufenacil (1 g ha −1 ) provided enhanced herbicidal activity compared with the products applied in idually on Palmer amaranth ( Amaranthus palmeri S. Watson). The synergism between the two herbicides was also confirmed by isobole analysis and field trials. The herbicide combination provided high levels of efficacy when applied at low temperature and low humidity. Mechanistically, glufosinate caused a transient accumulation of glutamate, the building block for chlorophyll biosynthesis. Consequently, inhibition of both GS and PPO resulted in greater accumulation of protoporphyrin and ROS, forming the physiological basis for the synergism between glufosinate and PPO inhibitors. While the synergy between the two herbicide MoAs provided excellent efficacy on weeds, it caused low injury to PPO-resistant waterhemp [ Amaranthus tuberculatus (Moq.) Sauer] and high injury to both glufosinate-resistant and glufosinate-susceptible soybean [ Glycine max (L.) Merr.]. Glufosinate enhances the activity of PPO inhibitors through glutamate and protoporphyrin accumulation, leading to increased levels of ROS and lipid peroxidation. The synergism between the two herbicide MoAs can help to overcome environmental effects limiting the efficacy of glufosinate. Future research is needed to optimize the uses for this herbicidal composition across different cropping systems.
Publisher: Wiley
Date: 08-07-2005
Publisher: Cambridge University Press (CUP)
Date: 06-2016
Abstract: Rigid ryegrass, an important annual weed species in cropping regions of southern Australia, has evolved resistance to 11 major groups of herbicides. Dose–response studies were conducted to determine response of three clethodim-resistant populations and one clethodim-susceptible population of rigid ryegrass to three different frost treatments (−2 C). Clethodim-resistant and -susceptible plants were exposed to frost in a frost chamber from 4:00 P.M. to 8:00 A.M. for three nights before or after clethodim application and were compared with plants not exposed to frost. A reduction in the level of clethodim efficacy was observed in resistant populations when plants were exposed to frost for three nights before or after clethodim application. In the highly resistant populations, the survival percentage and LD 50 were higher when plants were exposed to frost before clethodim application compared with frost after clethodim application. However, frost treatment did not influence clethodim efficacy of the susceptible population. Sequencing of the acetyl coenzyme A carboxylase (ACCase) gene of the three resistant populations identified three known mutations at positions 1781, 2041, and 2078. However, most in iduals in the highly resistant populations did not contain any known mutation in ACCase, suggesting the resistance mechanism was a nontarget site. The effect of frost on clethodim efficacy in resistant plants may be an outcome of the interaction between frost and the clethodim resistance mechanism(s) present.
Publisher: Cambridge University Press (CUP)
Date: 09-2002
Publisher: Wiley
Date: 12-06-2018
DOI: 10.1002/PS.5048
Abstract: There have been previous calls for, and efforts focused on, realizing the power and potential of weed genomics for better understanding of weeds. Sustained advances in genome sequencing and assembly technologies now make it possible for in idual research groups to generate reference genomes for multiple weed species at reasonable costs. Here, we present the outcomes from several meetings, discussions, and workshops focused on establishing an International Weed Genomics Consortium (IWGC) for a coordinated international effort in weed genomics. We review the 'state of the art' in genomics and weed genomics, including technologies, applications, and on-going weed genome projects. We also report the outcomes from a workshop and a global survey of the weed science community to identify priority species, key biological questions, and weed management applications that can be addressed through greater availability of, and access to, genomic resources. Major focus areas include the evolution of herbicide resistance and weedy traits, the development of molecular diagnostics, and the identification of novel targets and approaches for weed management. There is increasing interest in, and need for, weed genomics, and the establishment of the IWGC will provide the necessary global platform for communication and coordination of weed genomics research. © 2018 Society of Chemical Industry.
Publisher: Wiley
Date: 13-02-2017
DOI: 10.1002/PS.4512
Abstract: Chloris virgata is a warm-season, C Based on the rate of glyphosate required to kill 50% of treated plants (LD This report confirms glyphosate resistance in C. virgata and shows that target-site EPSPS mutations confer resistance to glyphosate in this species. The evolution of glyphosate resistance in C. virgata highlights the need to identify alternative control tactics. © 2016 Society of Chemical Industry.
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1614/WS-05-184R.1
Abstract: Several studies were conducted to evaluate the effects of different tillage systems on the vertical seed distribution, seedling recruitment pattern, and persistence of the rigid ryegrass seed bank. Experiments were conducted in South Australia at two locations (Roseworthy C us and Minlaton, a site on the Yorke Peninsula) in 2003 and 2005. The distribution of surface seeds through the soil profile was associated with the level of soil disturbance. The low–soil-disturbance tillage systems left more seed on the soil surface, whereas the high–soil-disturbance systems buried most of the seeds. The seedling recruitment of rigid ryegrass was lower under the low–soil-disturbance tillage systems than under the high–soil-disturbance tillage systems at both locations. The seedling recruitment was two- to fourfold greater under minimum tillage than under no-till. Not only was the seedling recruitment lower under the low–soil-disturbance tillage systems, biomass accumulation by rigid ryegrass seedlings was also lower under these systems. The carryover of residual viable seeds from one season to the next was similar between the tillage systems. However, seed decay under no-till (48 to 60%) was much greater than under minimum tillage (12 to 39%).
Publisher: Cambridge University Press (CUP)
Date: 06-2013
Abstract: A population of oriental mustard from Port Broughton in South Australia was reported as not being controlled by 2,4-D. Dose response experiments determined this population was resistant to both 2,4-D and MCPA, requiring greater than 20 times more herbicide for equivalent control compared to a known susceptible population (from Roseworthy, South Australia) and a population resistant only to the acetohydroxyacid synthase (AHAS)-inhibiting herbicides (from Tumby Bay, South Australia). The Port Broughton population was also found to be resistant to three chemical groups that inhibit AHAS however, the level of resistance was lower than the known acetolactate synthase–resistant population from Tumby Bay. Herbicides from other modes of action were able to control the Port Broughton population. Assays of isolated AHAS from the Port Broughton population showed high levels of resistance to the sulfonylurea and sulfonamide herbicide groups, but not to the imidazolinone herbicides. A single nucleotide change in the AHAS gene that predicted a Pro to Ser substitution at position 197 in the protein was identified in the Port Broughton population. This population of oriental mustard has evolved multiple resistance to AHAS-inhibiting herbicides (AHAS inhibitors) and auxinic herbicides, through a mutation in AHAS and a second nontarget-site mechanism. Whether the same mechanism provides resistance to both AHAS inhibitors and auxinic herbicides remains to be determined. Multiple resistance to auxinic herbicides and AHAS inhibitors in the Port Broughton population will make control of this population more difficult.
Publisher: Wiley
Date: 03-1998
Publisher: Wiley
Date: 21-07-2010
Publisher: Cambridge University Press (CUP)
Date: 05-2004
DOI: 10.1614/P2002-168B
Publisher: Cambridge University Press (CUP)
Date: 09-2012
Abstract: Herbicide resistance in rigid ryegrass is an escalating problem in grain-cropping fields of southeastern Australia due to increased reliance on herbicides as the main method for weed control. Weed surveys were conducted between 1998 and 2009 to identify the extent of herbicide-resistant rigid ryegrass across this region to dinitroaniline, and acetolactate synthase- and acetyl coenzyme A (CoA) carboxylase-inhibiting herbicides. Rigid ryegrass was collected from cropped fields chosen at random. Outdoor pot studies were conducted during the normal winter growing season for rigid ryegrass with PRE-applied trifluralin and POST-applied diclofop-methyl, chlorsulfuron, tralkoxydim, pinoxaden, and clethodim. Herbicide resistance to trifluralin in rigid ryegrass was identified in one-third of the fields surveyed from South Australia, whereas less than 5% of fields in Victoria exhibited resistance. In contrast, resistance to chlorsulfuron was detected in at least half of the cropped fields across southeastern Australia. Resistance to the cereal-selective aryloxyphenoxypropionate-inhibiting herbicides diclofop-methyl, tralkoxydim, and pinoxaden ranged between 30 and 60% in most regions, whereas in marginal cropping areas less than 12% of fields exhibited resistance. Resistance to clethodim varied between 0 and 61%. Higher levels of resistance to clethodim were identified in the more intensively cropped, higher-rainfall districts where pulse and canola crops are common. These weed surveys demonstrated that a high incidence of resistance to most tested herbicides was present in rigid ryegrass from cropped fields in southeastern Australia, which presents a major challenge for crop producers.
Publisher: CSIRO Publishing
Date: 2023
DOI: 10.1071/CP22386
Publisher: Springer Science and Business Media LLC
Date: 05-11-2014
DOI: 10.1007/S00425-014-2197-9
Abstract: Field-evolved resistance to the herbicide glyphosate is due to lification of one of two EPSPS alleles, increasing transcription and protein with no splice variants or effects on other pathway genes. The widely used herbicide glyphosate inhibits the shikimate pathway enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Globally, the intensive use of glyphosate for weed control has selected for glyphosate resistance in 31 weed species. Populations of suspected glyphosate-resistant Kochia scoparia were collected from fields located in the US central Great Plains. Glyphosate dose response verified glyphosate resistance in nine populations. The mechanism of resistance to glyphosate was investigated using targeted sequencing, quantitative PCR, immunoblotting, and whole transcriptome de novo sequencing to characterize the sequence and expression of EPSPS. Sequence analysis showed no mutation of the EPSPS Pro106 codon in glyphosate-resistant K. scoparia, whereas EPSPS genomic copy number and transcript abundance were elevated three- to ten-fold in resistant in iduals relative to susceptible in iduals. Glyphosate-resistant in iduals with increased relative EPSPS copy numbers had consistently lower shikimate accumulation in leaf disks treated with 100 μM glyphosate and EPSPS protein levels were higher in glyphosate-resistant in iduals with increased gene copy number compared to glyphosate-susceptible in iduals. RNA sequence analysis revealed seven nucleotide positions with two different expressed alleles in glyphosate-susceptible reads. However, one nucleotide at the seven positions was predominant in glyphosate-resistant sequences, suggesting that only one of two EPSPS alleles was lified in glyphosate-resistant in iduals. No alternatively spliced EPSPS transcripts were detected. Expression of five other genes in the chorismate pathway was unaffected in glyphosate-resistant in iduals with increased EPSPS expression. These results indicate increased EPSPS expression is a mechanism for glyphosate resistance in these K. scoparia populations.
Publisher: Wiley
Date: 17-10-2001
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CP19537
Abstract: Conyza bonariensis (L.) Cronq. (syn. of Erigeron bonariensis L.) is a difficult-to-control summer weed species in the cropping belt of south-eastern Australia. Herbicide resistance may be affecting the ability to control C. bonariensis in the agricultural region of north-eastern Victoria therefore, a survey was conducted to evaluate resistance to herbicides from several mode-of-action groups. Of the populations collected, 40% were resistant to glyphosate at 1080 g ha–1. Chlorsulfuron failed to control any of the populations collected. Further research identified multiple herbicide resistance to glyphosate, chlorsulfuron, metsulfuron-methyl and sulfometuron-methyl in five of nine populations fully characterised. Resistance was not found to 2,4-D, clopyralid or paraquat. There was no correlation between prevailing land use and the frequency of glyphosate-resistant populations, suggesting that resistance had been selected in multiple production systems. The high frequency of resistance could explain the difficulty experienced in controlling C. bonariensis across north-eastern Victoria and demonstrates the importance of integrated weed management to manage this weed.
Publisher: Elsevier BV
Date: 12-1987
Publisher: Cambridge University Press (CUP)
Date: 12-2015
Abstract: Clethodim resistance was identified in 12 rigid ryegrass populations from winter cropping regions in four different states of Australia. Clethodim had failed to provide effective control of these populations in the field and resistance was suspected. Dose–response experiments confirmed resistance to clethodim and butroxydim in all populations. During 2012, the LD 50 of resistant populations ranged from 10.2 to 89.3 g ha −1 , making them 3 to 34–fold more resistant to clethodim than the susceptible population. Similarly, GR 50 of resistant population varied from 8 to 37.1 g ha −1 , which is 3 to 13.9–fold higher than the susceptible population. In 2013, clethodim-resistant populations were 7.8 to 35.3–fold more resistant to clethodim than the susceptible population. The higher resistance factor in 2013, especially in moderately resistant populations, could have been associated with lower ambient temperatures during the winter of 2013. These resistant populations had also evolved cross-resistance to butroxydim. The resistant populations required 1.3 to 6.6–fold higher butroxydim dose to achieve 50% mortality and 3 to 27–fold more butroxydim for 50% biomass reduction compared to the standard susceptible population. Sequencing of the target-site ACCase gene identified five known ACCase substitutions (isoleucine-1781-leucine, isoleucine-2041-asparagine, aspartate-2078-glycine, and cysteine-2088-arginine, and glycine-2096-alanine) in these populations. In nine populations, multiple ACCase mutations were present in different in iduals. Furthermore, two alleles with different mutations were present in a single plant of rigid ryegrass in two populations.
Publisher: Cambridge University Press (CUP)
Date: 06-2015
Abstract: Acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides affect fatty acid biosynthesis in plants and are widely used to control smooth and hare barley in dicot crops in Australia. Recently, growers have experienced difficulty in controlling smooth and hare barley with herbicides from this mode of action. Dose–response experiments conducted on five suspected resistant populations confirmed varying levels of resistance to quizalofop and haloxyfop. The level of resistance in these populations was greater than 27-fold to quizalofop and greater than 15-fold to haloxyfop. The quizalofop dose required to reduce shoot biomass by 50% (GR 50 ) for the resistant populations varied from 52.6 to 111.9 g ha −1 , and for haloxyfop from 26.5 to 71.3 g ha −1 . Sequencing the CT domain of the ACCase gene from resistant plants of different populations confirmed the presence of previously known mutations Ile1781Leu and Gly2096Ala. Amino acid substitution at the 2096 position conferred a greater level of resistance to haloxyfop than the substitution at the 1781 position. This study documents the first known case of field-evolved target-site resistance to ACCase-inhibiting herbicides in Australian populations of smooth barley.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/CP17116
Abstract: Glyphosate-tolerant (GT) cotton offers a multitude of benefits such as broad-spectrum and cost-effective weed control, simple weed management, and reduced impact on the environment. However, high adoption rates of GT cotton have led to overreliance on glyphosate in weed management and have decreased the use of other herbicide options and non-chemical weed-management strategies, possibly leading to the emergence of many resistant weeds. Previous surveys in 2006 and 2011 in the cotton-growing regions of New South Wales (NSW) and Queensland, Australia, indicated changes in weed populations over the period and increased prevalence of several weeds. These two surveys indicated increased dominance of Conyza bonariensis, Echinochloa colona, and Chloris virgata in these regions. Periodic weed surveys are necessary to assess weed population dynamics and shifts due to overreliance on glyphosate for weed management. A survey was carried out in the cotton-growing regions of NSW and Queensland in 2014–15, covering 135 fields. Survey results indicated the emergence of volunteer GT cotton as the most common weed present across all of the cotton-growing regions, occurring in 85% of fields, followed by E. colona (67% of fields surveyed), and C. bonariensis and Sonchus oleraceus, which were present in 51% of fields. The most prevalent grass weed after E. colona was C. virgata (37%). Broadleaf weeds Ipomoea lonchophylla and Amaranthus mitchellii were present in 40% and 37% of fields, respectively. Regional-level analysis indicated greater prevalence of Sesbania cannabina and Parthenium hysterophorus in Emerald region of Queensland. Lolium rigidum was present in the Griffith and Warren area of NSW during summer, even though it is a winter weed. The results of this study indicate integration of ersified weed-management options and inclusion of both non-chemical and chemical options because many major weeds observed in this study are tolerant to glyphosate and have already evolved resistance to glyphosate.
Publisher: Wiley
Date: 10-1993
Publisher: Wiley
Date: 15-02-2017
DOI: 10.1002/PS.4501
Abstract: Acetyl coenzyme-A carboxylase (ACCase) and/or acetolactate synthase (ALS) inhibitor resistance has been identified by herbicide resistance screening in eight populations obtained from cropping regions of South Australia. This study aimed to quantify the level of resistance and characterise the molecular basis of resistance to ACCase and ALS inhibitors in these H. glaucum populations. H. glaucum populations from the Upper-North region were highly resistant (resistance index RI > 12) to the aryloxyphenoxypropionate (APP) herbicides quizalofop and haloxyfop and less resistant (RI = 2-12) to cyclohexanedione (CHD) herbicide clethodim, and some Mid-North populations had a low level of resistance (RI = 2-6) to the sulfonylurea (SU) herbicide mesosulfuron. Gene sequencing confirmed the presence of Ile-1781-Leu, Ile-2041-Asn and Gly-2096-Ala mutations in the ACCase gene, with no mutation found in the ALS gene. The use of the known metabolic inhibitor malathion in combination with mesosulfuron enhanced the activity of this herbicide. These populations were also susceptible to SU herbicide sulfometuron. This study has documented APP-to-CHD herbicide cross-resistance, the first case of ACCase inhibitor resistance due to Ile-2041-Asn mutation, and characterised the resistance to ALS inhibitors in H. glaucum. Resistance to ACCase inhibitors is due to a target-site mutation. The reversal of SU resistance by malathion and susceptibility to sulfometuron suggests that non-target-site mechanisms confer resistance to ALS inhibitors. © 2016 Society of Chemical Industry.
Publisher: Wiley
Date: 03-2007
Publisher: Springer Science and Business Media LLC
Date: 1989
DOI: 10.1007/BF00114770
Publisher: Cambridge University Press (CUP)
Date: 05-2017
DOI: 10.1017/WSC.2017.5
Abstract: Windmillgrass is a major weed in agricultural systems in northern Australia, and it has now become more common in southern Australia. Because little information is available on the biology of this weed species in southern Australia, studies were conducted to investigate plant development and seed biology. Under irrigated field conditions in South Australia, windmillgrass required 748 to 786 growing degree days from emergence to mature seed production. Freshly harvested seed had low dormancy with 16% to 40% germination. Seeds required light exposure for germination and less than 2% germination was observed in complete darkness. Seed could germinate over a wide temperature range (10 to 40 C) with maximum germination at 20 to 25 C. At 25 to 30 C, 50% germination occurred within 27.3 to 45.5 h, and the predicted base temperature for germination of the two populations investigated ranged from 9.2 to 11.2 C. The sodium chloride concentration and osmotic potential required to inhibit germination by 50% were 51 to 73 mM and −0.27 MPa, respectively. Seedling emergence was completely inhibited by burial of seed, which is consistent with its absolute requirement for light exposure to begin germination. Under field conditions, there was no clear effect of burial depth on seed viability in the first 2 yr with average rainfall, and seeds were completely nonviable after 12 mo. However, in the third year, with low spring–summer rainfall, buried seeds (37% viability after 14 mo) persisted longer than those left on the soil surface (6% viability after 14 mo). This study provides important information on plant development and seed biology of windmillgrass that will contribute to the development of a management program for this weed species in southern Australia.
Publisher: Elsevier BV
Date: 02-1997
Publisher: Wiley
Date: 24-02-2014
DOI: 10.1002/PS.3728
Abstract: Two major classes of herbicides include inhibitors of protoporphyrinogen oxidase (PPO) and phytoene desaturase (PDS). Plants can evolve resistance to PPO and PDS inhibitors via several mechanisms that include physical changes, resulting in reduced uptake, physiological changes, resulting in compartmentalization or altered translocation, and biochemical changes, resulting in enhanced metabolic degradation or alterations of protein structures, leading to loss of sensitivity to the herbicides. This review discusses the involvement of some of these mechanisms in the various cases of resistance to PDS- and PPO-inhibiting herbicides, and highlights unique aspects of target-site resistance to these herbicides.
Publisher: Wiley
Date: 17-10-2017
DOI: 10.1111/WBM.12133
Publisher: Wiley
Date: 20-05-1985
Publisher: Elsevier
Date: 1996
Publisher: Cambridge University Press (CUP)
Date: 03-2007
DOI: 10.1614/WT-06-044.1
Abstract: The efficacy of metolachlor on rigid ryegrass was determined under a no-till seeding system in an experiment conducted in 2004 and 2005 in South Australia. Metolachlor at a rate of 0.48 and 0.96 kg ai/ha was applied at 40 or 46 d (very early preplant, VEPP) and 20 or 23 d before crop sowing (early preplant, EPP), and at sowing (preplant, PP) in 2004 and 2005 the herbicide was incorporated by sowing. The control of rigid ryegrass was greater than 80% when metolachlor was applied PP however, that application resulted in phytotoxic effects on emergence and yield of wheat metolachlor was more phytotoxic when applied at 0.96 kg/ha than at 0.48 kg/ha. Metolachlor applied EPP provided 71 to 83% rigid ryegrass control, whereas VEPP application provided only 33 to 49% control. Reduction in wheat grain yield was not observed at these application times. This study indicates that metolachlor at 0.48 kg/ha could be safely applied around 20 d before crop sowing to selectively control rigid ryegrass in wheat.
Publisher: Cambridge University Press (CUP)
Date: 06-2014
Abstract: Field experiments were conducted in 2008, 2011, and 2012 to investigate the interaction between seeding system disturbance and PPI herbicides on rigid ryegrass control in wheat. Of the herbicides examined, prosulfocarb + S -metolachlor, and pyroxasulfone provided ≥ 70% control of rigid ryegrass, irrespective of seeding system. In contrast, trifluralin was the least-effective herbicide against rigid ryegrass and was particularly ineffective when used with single disc (10% control) relative to the triple-disc seeding system (80%) in 2012. Trifluralin consistently reduced wheat density when incorporated using single discs (46 to 59%) but not do so with the triple disc or double-shoot knife-point systems. Although there were large differences in crop establishment because of herbicide phytotoxicity, that did not always translate into large differences in yield because wheat was able to recover from reductions in plant density by increasing the spike number per plant. Pyroxasulfone caused no damage to wheat and appeared to be the most suitable PPI herbicide for use with single-disc seeding systems.
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/EA05291
Abstract: In the past few years, there has been a growing trend towards reducing tillage in cropping systems to allow stubble retention, earlier planting and improved soil structure. However, the adoption of conservation tillage systems will change weed control practices. Different tillage systems interact with the micro-environment of weed seeds and can influence the pattern of recruitment from the weed seed bank. Here, we present a review of the effect of different tillage systems on weed ecology, herbicide activity and herbicide persistence. Tillage systems can have a major influence on the vertical distribution of weed seeds in the soil seed bank. However, the impact of the changes in the vertical seed distribution on weed seedling recruitment is not well understood. Usually weed seedling recruitment increases if tillage equipment brings buried seed to, or close to, the soil surface, and seedling recruitment decreases if surface seed is buried deeper in the soil. However, tillage responses have a tendency to be species specific and can also be influenced by the intensity of tillage. Any weed species in which germination is stimulated by exposure to light is likely to become more prevalent under reduced tillage systems. Similarly, species that require burial for germination may become less prevalent. Crop residue present on the soil surface can also influence weed seedling recruitment by modifying the physical environment (mainly temperature) of weed seeds. Weed responses to plant residue could also be influenced by the allelopathic activity of the residue and the sensitivity of the weed species present. Few studies have investigated the fate of weed seeds that fail to germinate under any tillage system. Further research is needed to determine whether the weed seeds that fail to germinate decay before the start of the next growing season or become part of a persistent seed bank. Crop residues present on the soil surface can intercept a considerable amount of the applied herbicide and, depending on the herbicide, this intercepted component is susceptible to losses. Therefore, conservation tillage systems are expected to have lower efficacy of soil active herbicides. However, there has been little investigation of rate of loss of soil active herbicides under reduced tillage systems and the results reported have been inconsistent. Much of the research on these effects is from overseas and may not be true in Australian conditions. Therefore, further work is needed to clearly understand the impact of changing tillage systems on weed ecology, herbicide performance and persistence.
Publisher: Wiley
Date: 04-01-2017
DOI: 10.1002/PS.4493
Abstract: In Australia, the extensive use of clethodim for the control of Lolium rigidum has resulted in the evolution of many clethodim-resistant L. rigidum populations. Five clethodim-resistant populations of L. rigidum were analysed for the inheritance of clethodim resistance. Reciprocal crosses were made between resistant (R) and susceptible (S) populations. Within crosses, dose-responses of reciprocal F The results of this study indicate that different patterns of clethodim resistance in L. rigidum exist. © 2016 Society of Chemical Industry.
Publisher: Elsevier BV
Date: 09-2016
Publisher: Springer Science and Business Media LLC
Date: 1989
DOI: 10.1007/BF00114769
Publisher: Cambridge University Press (CUP)
Date: 2005
DOI: 10.1614/WS-03-140R
Publisher: Cambridge University Press (CUP)
Date: 10-2006
DOI: 10.1614/WS-06-061R.1
Abstract: Threehorn bedstraw is an important dicotyledonous weed of winter crops in southern Australia, which can be difficult to control in some field crops. Knowledge of the germination ecology of this weed would facilitate development of effective weed control programs. Seed germination in the laboratory was greater for seeds that after-ripened while buried in the soil relative to those that after-ripened on the soil surface. The timing of greatest seed germination in the laboratory was found to coincide with the period of low temperature in the field. Seed germination of threehorn bedstraw was moderately sensitive to salt stress but moderately tolerant to osmotic stress. Seeds of threehorn bedstraw germinated over a broad range of pH from 4 to 10. No seedlings emerged from seeds placed on the soil surface. Maximum seedling emergence occurred at depths of 1 to 2 cm (89 to 91%) and declined at greater depths.
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.
Publisher: Wiley
Date: 30-12-2015
DOI: 10.1002/PS.3956
Abstract: A population of Sisymbrium orientale from South Australia has multiple resistance to auxinic herbicides and inhibitors of acetohydroxyacid synthase (AHAS). Inheritance of resistance to 2,4-D and chlorsulfuron was studied in this population. Crosses were made between seven resistant in iduals as pollen donors to seven susceptible in iduals. Sixteen F1 in iduals from three crosses were identified by their lack of strong epinasty when treated with 200 g 2,4-D ha(-1). These in iduals were selfed, and segregation analysis of strong epinasty in the resulting progeny fitted a 3:1 ratio for resistant:susceptible in iduals when treated with 200 g 2,4-D ha(-1), as predicted by a single major gene. A detailed dose-response analysis of the F2 populations to 2,4-D confirmed single-gene inheritance. Analysis of segregation to 1 g chlorsulfuron ha(-1), a concentration that kills all susceptible in iduals, was unable to determine the mode of inheritance. A detailed dose-response analysis indicated that two genes contributed to chlorsulfuron resistance: a dominant target-site mutation of Pro 197 to Ser and a second gene with dose-dependent dominance. This population has a single dominant allele conferring 2,4-D resistance, whereas two genes contribute to chlorsulfuron resistance. Single dominant gene inheritance demonstrates that 2,4-D resistance can be readily selected.
Publisher: Wiley
Date: 14-09-2009
Publisher: Springer Science and Business Media LLC
Date: 05-05-2020
Publisher: Elsevier BV
Date: 07-1994
Publisher: Elsevier BV
Date: 03-2006
Publisher: Wiley
Date: 10-2005
Publisher: CSIRO Publishing
Date: 07-2022
DOI: 10.1071/CP22088
Abstract: Context Lolium rigidum Gaudin (annual ryegrass) has remained the most problematic weed of crop production in Australia for more than 20 years. There is some evidence that this weed species can rapidly adapt to management practices including delayed crop sowing. Aims Studies were undertaken to determine genetic variation for seed dormancy within L. rigidum populations and its association with genes involved with gibberellic acid and abscisic acid synthesis. Methodology Populations of L. rigidum were grown in pots to select low and high dormancy cohorts. Seeds produced by these cohorts from each population were assessed for variation in seed dormancy. Seeds of high and low dormancy cohorts were concurrently assessed for seed dormancy and expression of LrABA1 and LrGA20ox genes, using quantitative real-time PCR. Results Presence of differences greater than two-fold in seed dormancy between populations from the same farm indicated in situ selection for seed dormancy, most likely in response to management. Low and high dormancy cohorts of all populations maintained clear differences in seed dormancy in both years of assessment. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with LrABA1 and LrGA20ox gene expression. Conclusions This investigation has provided clear evidence of the presence of genetic variation for seed dormancy within L. rigidum populations. Implications The presence of genetic variation for seed dormancy in L. rigidum populations will allow this weed to adapt rapidly to changes in weed management practices such as delayed sowing of crops.
Publisher: Wiley
Date: 25-11-2004
Publisher: Cambridge University Press (CUP)
Date: 2008
DOI: 10.1614/WT-07-127.1
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1614/WS-05-156R.1
Abstract: Pollen movement between in iduals can increase the rate of herbicide resistance evolution by spreading resistance alleles within or between populations and by facilitating the rapid accumulation of resistance alleles within in iduals. This study investigated the level of pollen-mediated gene flow between paraquat-resistant and paraquat-susceptible populations of the self-pollinated weed species hare barley. The experiment was conducted in both directions, from resistant to susceptible and susceptible to resistant, across 2 yr. To maximize the potential for pollen flow, in idual plants were grown in a single pot. The level of gene flow was similar across years and between genotypes. The level of pollen-mediated gene flow ranged from 0.06 to 0.15%. Gene flow from resistant to susceptible plants was confirmed by demonstrating segregation for resistance in the progeny of suspected crosses. This study suggests that pollen-mediated gene flow will occur in this species at frequencies less than 0.16% and could assist the accumulation of resistance alleles within a population. These low levels of gene flow through pollen movement suggest that cross-pollination over larger distances would be unlikely and pollen movement probably does not contribute to gene flow between populations.
Publisher: CSIRO Publishing
Date: 28-06-2022
DOI: 10.1071/CP22118
Abstract: Context Bromus diandrus Roth is a serious weed of cereal-based cropping systems in South Australia. Its adaptation to local climate and production systems, prolific seed production and evolution of herbicide resistance have made this weed difficult to manage. Aims Studies were undertaken to determine genetic variation in seed dormancy within B. diandrus populations and its association with genes involved with gibberellic acid and abscisic acid synthesis. Methodology Seeds from five B. diandrus populations were s led during 2017 from commercial fields and planted during 2018 in pots. Protracted seedling emergence in these populations allowed selection of low and high dormancy cohorts. Seeds produced by these cohorts from each population were evaluated for variation in seed dormancy in the following year. The process of cohort selection and seed dormancy evaluation was repeated. The mechanism regulating seed dormancy was investigated in 2020 by assessing seeds of low and high dormancy cohorts concurrently for dormancy and for expression of ABA1 and GA20ox genes, using quantitative real-time PCR. Results There was at least a two-fold difference in seed dormancy among populations collected from different farms. Low and high dormancy cohorts within each population maintained consistent differences in seed dormancy in both years of assessment, suggesting genetic control over this trait. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with ABA1 and GA20ox gene expression. Conclusions Large differences in seed dormancy exist between in iduals in B. diandrus populations. The study has provided evidence of genetic variation for seed dormancy within B. diandrus populations, which was associated with ABA1 and GA20ox gene expression. Implications Presence of genetic variation for seed dormancy could play an important role in adaptation to escape pre-sowing weed-control tactics, meaning that B. diandrus could become an even greater problem in field crops grown in this region.
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CP14066
Abstract: The repeated use of glyphosate to control annual ryegrass along fence lines and crop margins has resulted in the evolution of resistance to this herbicide in populations of annual ryegrass (Lolium rigidum) in cropping regions of Australia. Field trials were conducted between 2009 and 2011 at four fence-line sites in South Australia to identify suitable herbicide treatments for controlling glyphosate-resistant annual ryegrass. Annual ryegrass populations growing at all four sites were found to have 12–24-fold resistance to glyphosate compared with a standard susceptible population in dose-response experiments. Glyphosate alone (1080 g ha–1) did not effectively control glyphosate-resistant annual ryegrass at any location. Single applications of paraquat + diquat and paraquat + amitrole were effective where weed populations were low, with up to 99% reduction in seed-head production. Mixtures of paraquat + diquat + diuron, glufosinate ammonium + diuron and two applications of paraquat + diquat 14 days apart consistently provided high levels of control of glyphosate-resistant annual ryegrass at all locations, with % reduction in seed-head production. In 2011, glyphosate resistant in iduals of annual ryegrass were identified up to 50 m inside the fields adjacent to the fence. Therefore, failure to control glyphosate-resistant annual ryegrass along crop margins risks movement of resistance into adjacent cropped fields.
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/EA05163
Abstract: Forty growers in 4 major cotton-growing regions in Australia were surveyed in 2003 to investigate how the adoption of glyphosate-tolerant cotton (Roundup Ready) had influenced herbicide use, weed management techniques, and whether changes to the weed spectrum could be identified. The 10 most common weeds reported on cotton fields were the same in glyphosate-tolerant and conventional fields in this survey. Herbicide use patterns were altered by the adoption of glyphosate-tolerant cotton with up to 6 times more glyphosate usage, but 21% fewer growers applying pre-emergence herbicides in glyphosate-tolerant fields. Other weed control practices such as the use of post-emergence herbicides, inter-row cultivation and hand hoeing were only reduced marginally. However, growers indicated that management practices are likely to change over time, especially with the introduction of enhanced glyphosate tolerance technology (Roundup Ready Flex), and anticipate a 32% decrease in the number of growers using alternative weed management practices. To date, management practices other than glyphosate use have not changed markedly in glyphosate-tolerant cotton indicating a conservative approach by growers adopting this technology and reflecting the narrow window of herbicide application. The range of weed control options still being employed in glyphosate-tolerant cotton would not increase the risk of glyphosate resistance development.
Publisher: Elsevier BV
Date: 12-1985
Publisher: Wiley
Date: 09-2017
Publisher: Cambridge University Press (CUP)
Date: 06-2016
Abstract: Rigid ryegrass is the most-troublesome, herbicide-resistant weed in cropping systems of southern Australia. Field experiments were undertaken at Roseworthy, South Australia, in 2013 and 2014, to identify effective herbicide options for the control of clethodim-resistant rigid ryegrass in Clearfield canola. PPI trifluralin + triallate followed by (fb) POST imazamox + imazapyr + clethodim + butroxydim had the lowest plant density of rigid ryegrass in 2014 and provided superior control compared with the standard grower practice of PPI trifluralin + triallate fb POST imazamox + imazapyr + clethodim in 1 of 2 yr. Propyzamide either alone or as a split application (PPI fb POST) or in combination with clethodim provided similar rigid ryegrass control to that of the standard grower practice (38 to 553 plants m −2 ). Rigid ryegrass treated with PPI dimethenamid-P, pethoxamid, pethoxamid + triallate, and PPI trifluralin fb carbetamide POST produced significantly more seeds than the standard grower practice, which would lead to reinfestation of subsequent crops. Canola yield responded positively to effective herbicide treatments, especially in 2014, when rigid ryegrass density was greater. PPI dimethenamid-P and pethoxamid alone or in combination with triallate and propyzamide were ineffective in reducing rigid ryegrass density and seed production to levels acceptable for continuous cropping systems.
Publisher: Cambridge University Press (CUP)
Date: 06-02-2017
DOI: 10.1017/WSC.2016.33
Abstract: Feather fingergrass is a major weed in agricultural systems in northern Australia and has now spread to southern Australia. To better understand the biology of this emerging weed species, its growth, development, and seed biology were examined. Under field conditions in South Australia, seedlings that emerged after summer rainfall events required 1,200 growing degree days from emergence to mature seed production and produced 700 g m −2 shoot biomass. Plants produced up to 1,000 seeds panicle −1 and more than 40,000 seeds plant −1 , with seed weight ranging from 0.36 to 0.46 mg. Harvested seeds were dormant for a period of about 2 mo and required 5 mo of after-ripening to reach 50% germination. Freshly harvested seed could be released from dormancy by pretreatment with 564 mM sodium hypochlorite for 30 min. Light significantly increased germination. Seed could germinate over a wide temperature range (10 to 40 C), with maximum germination at 15 to 25 C. At 20 to 25 C, 50% germination was reached within 2.7 to 3.3 d, and the predicted base temperature to germinate was 2.1 to 3.0 C. The osmotic potential and NaCl concentration required to inhibit germination by 50% were −0.16 to −0.20 MPa and 90 to 124 mM, respectively. Seedling emergence was highest (76%) for seeds present on soil surface and was significantly reduced by burial at 1 (57%), 2 (49%), and 5 cm (9%). Under field conditions, seeds buried in the soil persisted longer than those left on the soil surface, and low spring–summer rainfall increased seed persistence. This study provides important information on growth, development, and seed biology of feather fingergrass that will contribute to the development of a more effective management program for this weed species in Australia.
Publisher: Elsevier BV
Date: 10-2005
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.CHEMOSPHERE.2010.03.046
Abstract: Imidazolinones are chiral herbicides, comprised of two enantiomers with differential herbicidal activity. In this study, the selective degradation of enantiomers of the three imidazolinone herbicides, imazapyr, imazethapyr and imazaquin, was determined in a variety of soils selected to cover a broad range of physico-chemical characteristics. The R(+) enantiomer of all three herbicides, which has greater herbicidal activity (up to eight times), was found to degrade faster than the less active S(-) enantiomer. The enantiomer fraction (EF) was used as a descriptor of enantio-selectivity of the imidazolinone herbicides. The EF values increased with increasing incubation time for imidazolinones with a fast initial phase followed by a slower phase. While the enantio-selectivity was not significant in acidic soils (pH(w) 5.02 and 5.20), it was highly significant (P<0.001) in alkaline soils (pH(w) 7.6, 8.2 and 8.7). Significant positive correlations of EF values of imazapyr (P<0.001, R(2)=0.41), imazethapyr (P<0.002, R(2)=0.47) and imazaquin (P<0.001, R(2)=0.54) were found with the soil pH(w) ranging from 5.02 to 8.7. However, no correlation of EF was found with other soil properties. In addition to showing enantioselective degradation of the three herbicides in the soils studied, the study highlighted that for imidazolinones the herbicidally more active enantiomer can be preferably degraded by microorganisms.
No related grants have been discovered for Christopher Preston.