ORCID Profile
0000-0001-6964-2499
Current Organisation
Colorado State University
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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: Cambridge University Press (CUP)
Date: 10-2001
Publisher: Cambridge University Press (CUP)
Date: 10-2001
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: 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: Public Library of Science (PLoS)
Date: 10-09-2020
Publisher: Elsevier BV
Date: 11-2023
Publisher: American Physical Society (APS)
Date: 14-04-2023
Publisher: Elsevier BV
Date: 07-2020
Publisher: Cold Spring Harbor Laboratory
Date: 31-08-2023
DOI: 10.1101/2023.08.29.554743
Abstract: Auxin-mimic herbicides chemically mimic the phytohormone indole-3-acetic-acid (IAA). Within the auxin-mimic herbicide class, the herbicide fluroxypyr has been extensively used to control an agronomically problematic Great Plains tumbleweed, kochia (Bassia scoparia). A 2014 field survey for herbicide resistance in kochia populations across Colorado identified a putative fluroxypyr resistant population that was assessed for response to five different herbicides representing four different herbicide modes of action. These included fluroxypyr and dicamba (auxin-mimics), atrazine (photosystem II inhibitor), glyphosate (EPSPS inhibitor), and chlorsulfuron (acetolactate synthase inhibitor). The greenhouse screen identified that this kochia population was resistant to fluroxypyr and chlorsulfuron, but sensitive to glyphosate, atrazine, and dicamba. This population was designated Flur-R. Subsequent dose response studies determined that 75% of the Flur-R population survived 628 g ae ha-1 of fluroxypyr (4x the label application rate in wheat fallow, which is 157 g ae ha-1 at 1x). Flur-R was 40 times more resistant to fluroxypyr than a susceptible population (J01-S) collected from the same field survey (LD50 720 and 20 g ae ha-1, respectively). Auxin-responsive gene expression increased following fluroxypyr treatment in Flur-R, J01-S, and in a dicamba-resistant, fluroxypyr-susceptible line 9425 in an RNA-sequencing experiment. In Flur-R, several transcripts with molecular functions for conjugation and transport were constitutively higher expressed, such as glutathione S-transferases (GSTs), UDP-glucosyl transferase (GT), and ATP binding cassette transporters (ABC transporters). After analyzing metabolic profiles over time, both Flur-R and J01-S rapidly converted [14C]-fluroxypyr ester, the herbicide formulation applied to plants, to [14C]-fluroxypyr acid, the biologically active form of the herbicide, and three unknown metabolites. Formation and flux of these metabolites was faster in Flur-R than J01-S, reducing the concentration of phytotoxic fluroxypyr acid. One unique metabolite was present in Flur-R that was not present in the J01-S metabolic profile. Gene sequence variant analysis specifically for auxin receptor and signaling proteins revealed the absence of non-synonymous mutations affecting auxin signaling and binding in candidate auxin target site genes, further supporting our hypothesis that non-target site metabolic degradation is contributing to fluroxypyr resistance in Flur-R.
Publisher: MDPI AG
Date: 22-07-2020
Abstract: Wild poinsettia (Euphorbia heterophylla L.) is an important weed species in southern Brazil, especially due to the evolution of multiple herbicide resistance (e.g., acetolactate synthase (ALS)- inhibitors, protoporphyrinogen oxidase inhibitors, and glyphosate). The mechanism of resistance to imazamox was investigated in two wild poinsettia populations (R1 and R2) from southern Brazil and compared to a known susceptible (S) population. Imazamox dose-response experiments revealed high levels of resistance: 45-fold and 224.5-fold based on dry biomass reduction, for R1 and R2, respectively. Extremely high concentrations of imazamox (20,000 µM) were not sufficient to provide 50% inhibition of ALS enzyme activity (I50) for R1 or R2. Hence, resistance levels were estimated to be greater than 123-fold for both populations based on in vitro ALS assays. The ALS gene from all R1 and R2 plants had a Trp574Leu mutation. A genotyping assay was developed to discriminate resistant and susceptible alleles based on the Trp574Leu mutation.
Publisher: Wiley
Date: 11-09-2018
DOI: 10.1002/PS.5128
Publisher: Wiley
Date: 27-09-2017
DOI: 10.1002/PS.4697
Abstract: A population of Amaranthus tuberculatus (var. rudis) was confirmed resistant to 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitor herbicides (mesotrione, tembotrione, and topramezone) in a seed corn/soybean rotation in Nebraska. Further investigation confirmed a non-target-site resistance mechanism in this population. The main objective of this study was to explore the role of cytochrome P450 inhibitors in restoring the efficacy of HPPD-inhibitor herbicides on the HPPD-inhibitor resistant A. tuberculatus population from Nebraska, USA (HPPD-R). Enhanced metabolism via cytochrome P450 enzymes is the mechanism of resistance in HPPD-R. Amitrole partially restored the activity of mesotrione, whereas malathion, amitrole, and piperonyl butoxide restored the activity of tembotrione and topramezone in HPPD-R. Although corn was injured through malathion followed by mesotrione application a week after treatment, the injury was transient, and the crop recovered. The use of cytochrome P450 inhibitors with tembotrione may provide a new way of controlling HPPD-inhibitor resistant A. tuberculatus, but further research is needed to identify the cytochrome P450 candidate gene(s) conferring metabolism-based resistance. The results presented here aid to gain an insight into non-target-site resistance weed management strategies. © 2017 Society of Chemical Industry.
Publisher: American Physical Society (APS)
Date: 24-01-2023
Publisher: Springer Science and Business Media LLC
Date: 05-05-2020
Publisher: American Chemical Society (ACS)
Date: 12-2022
Abstract: A 2,4-dichlorophenoxyactic acid (2,4-D)-resistant population of
Publisher: American Physical Society (APS)
Date: 19-11-2021
Publisher: Cambridge University Press (CUP)
Date: 02-06-2020
DOI: 10.1017/WSC.2020.42
Abstract: Wild poinsettia ( Euphorbia heterophylla L.) is a troublesome broadleaf weed in grain production areas in South America. Herbicide resistance to multiple sites of action has been documented in this species, including protoporphyrinogen oxidase (PPO) inhibitors. We investigated the physiological and molecular bases for PPO-inhibitor resistance in a E. heterophylla population (R PPO ) from Southern Brazil. Whole-plant dose–response experiments revealed a cross-resistance profile to three different chemical groups of PPO inhibitors. Based on dose–response parameters, R PPO was resistant to lactofen (47.7-fold), saflufenacil (8.6-fold), and pyraflufen-ethyl (3.5-fold). Twenty-four hours after lactofen treatment (120 g ha −1 ) POST, R PPO accumulated 27 times less protoporphyrin than the susceptible population (S PPO ). In addition, R PPO generated 5 and 4.5 times less hydrogen peroxide and superoxide than S PPO , respectively. The chloroplast PPO ( PPO1 ) sequences were identical between the two populations, whereas 35 single-nucleotide polymorphisms were found for the mitochondrial PPO ( PPO2 ). Based on protein homology modeling, the Arg-128-Leu (homologous to Arg-98-Leu in common ragweed [ Ambrosia artemisiifolia L.] was the only one located near the catalytic site, also in a conserved region of PPO2 . The cytochrome P450 monooxygenase inhibitor malathion did not reverse resistance to lactofen in R PPO , and both populations showed similar levels of PPO1 and PPO2 expression, suggesting that metabolic resistance and PPO overexpression are unlikely. This is the first report of an Arg-128-Leu mutation in PPO2 conferring cross-resistance to PPO inhibitors in E. heterophylla .
Publisher: American Chemical Society (ACS)
Date: 19-06-1998
DOI: 10.1021/NP9800708
Publisher: American Chemical Society (ACS)
Date: 27-08-1998
DOI: 10.1021/NP980325H
Publisher: American Physical Society (APS)
Date: 17-08-2015
Publisher: American Chemical Society (ACS)
Date: 27-04-2023
Publisher: Wiley
Date: 17-09-2022
DOI: 10.1002/PS.7154
Abstract: Early detection of herbicide resistance in weeds is crucial for successful implementation of integrated weed management. We conducted a herbicide resistance survey of the winter annual grasses feral rye (Secale cereale), downy brome (Bromus tectorum), and jointed goatgrass (Aegilops cylindrica) from Colorado winter wheat production areas for resistance to imazamox and quizalofop. All s les were susceptible to quizalofop. All downy brome and jointed goatgrass s les were susceptible to imazamox. Out of 314 field collected s les, we identified three feral rye populations (named A, B, and C) that were imazamox resistant. Populations B and C had a target-site mechanism with mutations in the Ser653 residue of the acetolactate synthase (ALS) gene to Asn in B and to Thr in C. Both populations B and C had greatly reduced ALS in vitro enzyme inhibition by imazamox. ALS feral rye protein modeling showed that steric interactions induced by the amino acid substitutions at Ser653 impaired imazamox binding. In iduals from population A had no mutations in the ALS gene. The ALS enzyme from population A was equally sensitive to imazamox as to known susceptible feral rye populations. Imazamox was degraded two times faster in population A compared with a susceptible control. An oxidized imazamox metabolite formed faster in population A and this detoxification reaction was inhibited by malathion. Population A has a nontarget-site mechanism of enhanced imazamox metabolism that may be conferred by cytochrome P450 enzymes. This is the first report of both target-site and metabolism-based imazamox resistance in feral rye. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Publisher: Cambridge University Press (CUP)
Date: 18-12-2018
DOI: 10.1017/WSC.2018.71
Abstract: Glyphosate-resistant (GR) goosegrass [ Eleusine indica (L.) Gaertn.] was recently identified in Brazil, but its resistance mechanism was unknown. This study elucidated the resistance mechanism in this species and developed a molecular marker for rapid detection of this target-site resistance trait. The resistance factor for the resistant biotype was 4.4-fold compared with the glyphosate-susceptible (GS) in greenhouse dose–response experiments. This was accompanied by a similar (4-fold) difference in the levels of in vitro and in planta shikimate accumulation in these biotypes. However, there was no difference in uptake, translocation, or metabolism of glyphosate between the GS and GR biotypes. Moreover, both biotypes showed similar values for 5-enolpyruvylshikimate-3-phosphate synthase ( EPSPS ) copy number and transcription. Sequencing of a 330-bp fragment of the EPSPS gene identified a single-nucleotide polymorphism that led to a Pro-106-Ser amino acid substitution in the enzyme from the GR biotype. This mutation imparted a 3.8-fold increase in the amount of glyphosate required to inhibit 50% of EPSPS activity, confirming the role of this amino acid substitution in resistance to glyphosate. A quantitative PCR–based genotyping assay was developed for the rapid detection of resistant plants containing this Pro-106-Ser mutation.
Publisher: Wiley
Date: 12-08-2020
DOI: 10.1002/PS.5535
Abstract: Bidens subalternans (greater beggarticks) is a tetraploid and troublesome weed infesting annual crops in most tropical regions of the world. A glyphosate-resistant (GR) B. subalternans biotype was detected in a soybean field from Paraguay. A series of physiological and molecular analyses were conducted to elucidate its resistance mechanisms. The GR biotype had a high level of resistance (> 15-fold LD This is the first report of a TIPT double mutation conferring high levels of glyphosate resistance in a weed species. The presence of both wild-type and TIPT mutant EPSPS on the polyploid genome of GR B. subalternans may offset a potential fitness cost, requiring additional research to confirm the absence of deleterious effects. © 2019 Society of Chemical Industry.
Publisher: Wiley
Date: 28-02-2020
DOI: 10.1002/PS.5798
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
Location: Bangladesh
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
Start Date: 2018
End Date: 2022
Funder: Engineering and Physical Sciences Research Council
View Funded Activity