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Background: Italian ryegrass (Lolium multiflorum Lam.) is one of the most troublesome grass weeds in Argentina. The extensive and repetitive use of acetyl-CoA carboxylase (ACCase)-inhibiting herbicides has induced resistance in this weed species. The objectives of this study were to quantify the resistance levels to ACCase-inhibiting herbicides in two resistant populations and to identify the target-site mutations associated with their resistance., Results: Two resistant Italian ryegrass populations, Roldán and H2, were studied. Roldán was a suspected haloxyfop-resistant population, located in a wheat field from Santa Fe province with a history of ACCase-inhibiting herbicide use. The H2 population was obtained from the susceptible Hernandarias population (H0) after two cycles of selection with the herbicide quizalofop-ethyl. Whole-plant dose-response assays revealed that the resistant populations exhibited a high resistance to haloxyfop, with resistance factors (RF) exceeding 97-fold. Additionally, both populations showed a moderate resistance to pinoxaden (RF > 7), while maintaining susceptibility to clethodim. Partial chloroplastic ACCase sequences revealed isoleucine-to-asparagine substitution at position 2041 (Ile-2041-Asn) in both resistant populations., Conclusion: This work provides a better understanding of cross-resistance to ACCase-inhibiting herbicides in L. multiflorum populations and represents the first report of the target-site mutation Ile-2041-Asn conferring resistance in populations from Argentina. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Background: Chinese sprangletop [Leptochloa chinensis (L.) Nees] control is threatened by resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. In this study, a L. chinensis population, HFLJ18, that survived cyhalofop-butyl [aryloxyphenoxypropionate (APP) herbicide, CyB] treatment was collected from a rice field in Lujiang County, Anhui Province, China. This study aimed to evaluate the susceptibility of HFLJ18 to herbicides with different modes-of-action and investigate the potential mechanisms of resistance to CyB., Results: The HFLJ18 population exhibited high levels of resistance to CyB (10.92-fold) and showed resistance to the ACCase inhibitors metamifop (4.63-fold) and fenoxaprop-P-ethyl (8.39-fold), but was susceptible to clethodim, pinoxaden, florpyrauxifen-benzyl, oxadiazon and pretilachlor. Target gene sequencing revealed a novel Trp-to-Gly substitution at codon position 2027 of ACCase in the resistant plants. Molecular docking revealed that the spatial structure of ACCase changed significantly following the substitution, as indicated by reduced H-bonds. A newly derived cleaved amplified polymorphic sequence (dCAPS) marker was subsequently developed to detect the Trp-2027-Gly mutation in the ACCase of L. chinensis. Additionally, pretreatment with the cytochrome P450 (P450) inhibitor piperonyl butoxide (PBO) and the glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) did not reverse resistance to CyB, suggesting that nontarget-site resistance mechanisms were not involved in CyB resistance in the HFLJ18 population., Conclusion: Overall, the resistance to CyB in the HFLJ18 population derived from the mutation of ACCase gene, and to the best of our knowledge, this is the first report of the ACCase Trp-2027-Gly mutation conferring resistance to ACCase-inhibiting herbicides in grass species. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Background: Giant ragweed (Ambrosia trifida L.) is one of the most troublesome weed species in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] cropping systems. Following numerous reports in 2018 of suspected herbicide resistance in several Ambrosia trifida populations from Wisconsin, our objective was to characterize the response of these accessions to acetolactate synthase (ALS), enolpyruvyl shikimate phosphate synthase (EPSPS), and protoporphyrinogen oxidase (PPO) inhibitors applied POST., Results: Four accessions (AT1, AT4, AT6, and AT10) exhibited ≥ 50% plant survival after exposure to the cloransulam 3× rate. Two accessions (AT8 and AT10) and one accession (AT2) exhibited ≥ 50% plant survival after exposure to glyphosate and fomesafen 1× rates, respectively. The AT10 accession exhibited multiple resistance to cloransulam and glyphosate. The AT12 accession was 28.8-fold resistant to fomesafen and 3.7-fold resistant to lactofen. A codon change in PPX2 conferring a R98L substitution was identified as the most likely mechanism conferring PPO-inhibitor resistance., Conclusion: To our knowledge, this is the first confirmed case of PPO-inhibitor resistance in Ambrosia trifida globally and we identified the genetic mutation likely conferring resistance. Proactive and diversified integrated weed management strategies are of paramount importance for sustainable long-term Ambrosia trifida management. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

Background: Japanese brome (Bromus japonicus Thumb.) is one of the problematic annual weeds in winter wheat (Triticum aestivum L.) and is generally controlled by acetolactate synthase (ALS) inhibitors. Repeated use of the ALS inhibitor propoxycarbazone-Na resulted in the evolution of resistance to this herbicide in three B. japonicus populations, i.e., R1, R2, and R3 in Kansas (KS). However, the level of resistance and mechanism conferring resistance in these populations is unknown. The objectives of this research were to (i) evaluate the level of resistance to propoxycarbazone-Na in R1, R2, and R3 in comparison with a known susceptible population (S1), (ii) investigate the mechanism of resistance involved in conferring ALS-inhibitor resistance, and (iii) investigate the cross-resistance to other ALS inhibitors., Results: Dose-response (0 to 16x; x = 44 g ai ha -1 of propoxycarbazone-Na) assay indicated 167, 125, and 667-fold resistance in R1, R2 and R3 populations, respectively, compared to S1 population. ALS gene sequencing confirmed the mutations resulting in amino acid substitutions, i.e., Pro-197-Thr (R3, R1)/Ser (R2, R1) bestowing resistance to these ALS inhibitors. Such amino acid substitutions also showed differential cross-resistance to sulfosulfuron, mesosulfuron-methyl, pyroxsulam, and imazamox among resistant populations. Pretreatment with malathion (a cytochrome P450 enzyme-inhibitor) followed by imazamox treatment suggested cross-resistance to this herbicide possibly via metabolism only in R3 population., Conclusion: Overall, these results confirm the first case of target-site based resistance to ALS inhibitors in B. japonicus in the US, highlighting the need for exploring herbicides with alternative modes of action to enhance weed control in winter wheat. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Background: Chinese sprangletop (Leptochloa chinensis (L.) Nees) is an invasive grass weed severely infesting rice fields across China. In October 2020, a suspected resistant Leptochloa chinensis population HFFD3 that survived the acetyl-CoA carboxylase (ACCase)-inhibiting herbicide cyhalofop-butyl applied at its field-recommended rate was collected from a rice field in Feidong County, Anhui Province, China. This study aimed to determine the resistance profile of HFFD3 to ACCase inhibitors and to investigate its mechanisms of resistance to cyhalofop-butyl., Results: Single-dose testing confirmed that HFFD3 had evolved resistance to cyhalofop-butyl. Two loci encoding plastidic ACCase were each amplified from the susceptible (S) and resistant (R, HFFD3) individual plants. Target gene sequencing and derived cleaved amplified polymorphic sequence assay revealed all the R plants carried a Trp-2027-Leu substitution in their ACCase1,2 copies. Dose-response bioassays revealed that HFFD3 was highly resistant to cyhalofop-butyl and exhibited cross-resistance to metamifop, fenoxaprop-P-ethyl, quizalofop-P-ethyl, and clethodim. Pre-treatment with piperonyl butoxide and 4-chloro-7-nitrobenzoxadiazole considerably reversed the resistance of the R plants to cyhalofop-butyl, by 23% and 43%, respectively. Liquid chromatography-tandem mass spectrometry analysis suggested the metabolic rates of cyhalofop-butyl were significantly faster in the R than in the S plants., Conclusion: This study confirmed the first case of an arable weed species featuring cross-resistance to ACCase-inhibiting herbicides due to a novel Trp-2027-Leu mutation of ACCase. Target gene mutation and cytochrome P450s- and glutathione-S-transferases-involved enhanced metabolism may have simultaneously participated in the resistance of HFFD3 population to cyhalofop-butyl., (© 2021 Society of Chemical Industry.)

Background: Palmer amaranth (Amaranthus palmeri S. Wats) is one of the most common and troublesome weeds in the USA. Palmer amaranth resistance to acetolactate synthase (ALS) inhibitors is widespread in the USA, as in Arkansas. The cross-resistance patterns and mechanism of resistance are not known. Experiments were conducted to determine cross-resistance to ALS inhibitors and identify target-site mutations in 20 Palmer amaranth localities from 13 counties in Arkansas., Results: All Palmer amaranth localities tested had plants cross-resistant to imazethapyr, flumetsulam, primisulfuron, pyrithiobac and trifloxysulfuron. The dose of trifloxysulfuron that caused 50% control was 21-56-fold greater for resistant accessions than for susceptible ones. All but three resistant plants analyzed had one or two relative copies of ALS; one plant had seven relative copies. All resistant plants tested (18 localities) carried the Trp574Leu mutation, which is known to confer broad resistance to ALS inhibitors, supporting the cross-resistance pattern observed. Besides the Trp574Leu mutation, 30% of localities had individuals with one additional resistance-conferring mutation including Ala122Thr, Pro197Ala or Ser653Asn., Conclusion: The Trp574Leu mutation in ALS is the primary mechanism of resistance to ALS inhibitors in Palmer amaranth from Arkansas, USA. In some localities, multiple mutations have accumulated in one plant. All localities tested contained plants with resistance to five families of ALS inhibitors. Localities with extremely high resistance to ALS inhibitors, and those outside the subset we studied, may harbor non-target site resistance mechanisms. ALS inhibitors are generally no longer effective on Palmer amaranth in these localities from the US mid-south. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

A herbicide with a new mode of action has not been commercialized for more than 30 years. A recent paper describes a novel genomic approach to herbicide and herbicide mode of action discovery. Analysis of a microbial gene cluster revealed that it encodes genes for both the biosynthetic pathway for production of the sesquiterpene aspterric acid and an aspterric acid-resistant form of dihydroxy acid dehydratase (DHAD), its target enzyme. Aspterric acid is weak compared with commercial synthetic herbicides, and whether DHAD is a good herbicide target is unclear from this study. Nevertheless, this genomic approach provides a novel strategy for the discovery of herbicides with new modes action. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

Background: Resistance to the 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide tembotrione in an Amaranthus palmeri population from Nebraska (NER) has previously been confirmed to be attributable to enhanced metabolism. The objective of this study was to identify and quantify the metabolites formed in Nebraska susceptible (NES) and resistant (NER) biotypes., Results: NER and NES formed the same metabolites. Tembotrione metabolism in NER differed from that in NES in that resistant plants showed faster 4-hydroxylation followed by glycosylation. The T 50 value (time for 50% production of the maximum 4-hydroxylation product) was 4.9 and 11.9 h for NER and NES, respectively. This process is typically catalyzed by cytochrome P450 enzymes. Metabolism differences between NER and NES were most prominent under 28 °C conditions and herbicide application at the four-leaf stage., Conclusion: Further research with the aim of identifying the gene or genes responsible for conferring metabolic resistance to HPPD inhibitors should focus on cytochrome P450s. Such research is important because non-target-site-based resistance (NTSR) poses the threat of cross resistance to other chemical classes of HPPD inhibitors, other herbicide modes of action, or even unknown herbicides. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Protoporphyrinogen IX oxidase (PPO)-inhibiting herbicides are effective tools to control a broad spectrum of weeds, including those that have evolved resistance to glyphosate. Their utility is being threatened by the appearance of biotypes that are resistant to PPO inhibitors. While the chloroplastic PPO1 isoform is thought to be the primary target of PPO herbicides, evolved resistance mechanisms elucidated to date are associated with changes to the mitochondrial PPO2 isoform, suggesting that the importance of PPO2 has been underestimated. Our investigation of the evolutionary and structural biology of plant PPOs provides some insight into the potential reasons why PPO2 is the preferred target for evolution of resistance. The most common target-site mutation imparting resistance involved the deletion of a key glycine codon. The genetic environment that facilitates this deletion is apparently only present in the gene encoding PPO2 in a few species. Additionally, both species with this mutation (Amaranthus tuberculatus and Amaranthus palmeri) have dual targeting of PPO2 to both the chloroplast and the mitochondria, which might be a prerequisite to impart herbicide resistance. The most recent target-site mutations have substituted a key arginine residue involved in stabilizing the substrate in the catalytic domain of PPO2. This arginine is highly conserved across all plant PPOs, suggesting that its substitution could be equally likely on PPO1 and PPO2, yet it has only occurred on PPO2, underscoring the importance of this isoform for the evolution of herbicide resistance. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Background: Resistance to the synthetic auxin herbicide dicamba is increasingly problematic in Kochia scoparia. The resistance mechanism in an inbred dicamba-resistant K. scoparia line (9425R) was investigated using physiological and transcriptomics (RNA-Seq) approaches., Results: No differences were found in dicamba absorption or metabolism between 9425R and a dicamba-susceptible line, but 9425R was found to have significantly reduced dicamba translocation. Known auxin-responsive genes ACC synthase (ACS) and indole-3-acetic acid amino synthetase (GH3) were transcriptionally induced following dicamba treatment in dicamba-susceptible K. scoparia but not in 9425R. Chalcone synthase (CHS), the gene regulating synthesis of the flavonols quertecin and kaemperfol, was found to have twofold higher transcription in 9425R both without and 12 h after dicamba treatment. Increased CHS transcription co-segregated with dicamba resistance in a forward genetics screen using an F 2 population., Conclusion: Prior work has shown that the flavonols quertecin and kaemperfol compete with auxin for intercellular movement and vascular loading via ATP-binding cassette subfamily B (ABCB) membrane transporters. The results of this study support a model in which constitutively increased CHS expression in the meristem produces more flavonols that would compete with dicamba for intercellular transport by ABCB transporters, resulting in reduced dicamba translocation. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Background: 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)., Results: 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., Conclusion: 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., (© 2017 Society of Chemical Industry.)

Background: A field-evolved herbicide-resistant weed population can represent a heterogeneous composite of subpopulations that differ in their susceptibility and responsiveness to herbicide hormesis. Variable hormesis responsiveness can result in selection for and against certain subpopulations under low herbicide doses, and this has the potential to contribute to the evolution of resistance. The relevance of this hypothesis at practical field rates was studied for two field-collected acetyl-coenzyme A carboxylase (ACCase) target-site resistant (TSR) biotypes of Alopecurus myosuroides Huds. (haplotype Leu1781) exposed to three ACCase inhibitors. Herbicide dose responses were evaluated at the population level and at different subpopulation levels after the dissection of individual plants by herbicide selection and genotyping., Results: The practical field rates of fenoxaprop-P were lower than the observed hormetic doses in the resistant subpopulation, whereas the field rates of clodinafop and cycloxydim stimulated the shoot biomass in different resistant subpopulations by 21-38% above that of the control. Because variable dose levels induced hormesis in the different subpopulations, the practical field rates showed a significant potential to selectively enhance parts of a resistant field population, but did not impact or adversely affect other parts of the population., Conclusion: As a consequence of population heterogeneity, herbicide hormesis may impact resistance evolution in weeds at realistic use rates via the selective promotion of individual genotypes. However, the practical relevance of this phenomenon may be influenced by many factors, such as the herbicidal active ingredient used, as indicated in this study. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

Background: Crabgrass (Digitaria sanguinalis) is an annual monocotyledonous weed. In recent years, field applications of nicosulfuron have been ineffective in controlling crabgrass populations in Shandong Province, China. To investigate the mechanisms of resistance to nicosulfuron in crabgrass populations, the acetolactate synthase (ALS) gene fragment covering known resistance-confering mutation sites was amplified and sequenced., Results: Dose-response experiments suggested that the resistant population SD13 (R) was highly resistant to nicosulfuron (resistance index R/S = 43.7) compared with the sensitive population SD22 (S). ALS gene sequencing revealed a Trp574Arg substitution in the SD13 population, and no other known resistance-conferring mutations were found. In vitro ALS enzyme assays further confirmed that the SD13 population was resistant to all tested ALS-inhibiting herbicides. The resistance pattern experiments revealed that, compared with SD22, the SD13 population exhibited broad-spectrum resistance to nicosulfuron (43.7-fold), imazethapyr (11.4-fold) and flumetsulam (16.1-fold); however, it did not develop resistance to atrazine, mesotrione and topramezone., Conclusions: This study demonstrated that Trp574Arg substitution was the main reason for crabgrass resistance to ALS-inhibiting herbicides. To our knowledge, this is the first report of Trp574Arg substitution in a weed species, and is the first report of target-site mechanisms of herbicide resistance for crabgrass. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Background: The highly selective auxin-type herbicide quinclorac is widely used to control important dicotyledon and monocotyledon weeds in rice fields. Echinochloa crusgalli var. zelayensis is one of the most troublesome weeds in China, and is very difficult to control in east China due to misuse of herbicides., Results: The JZD -R, JTJ -R, JCW -R and SSX -R biotypes of E. crusgalli var. zelayensis had resistance to quinclorac with resistance levels ranked as JZD -R < JTJ -R < JCW -R < SSX -R. Growth reduction in different biotypes was positively correlated with ethylene production. Stimulated levels of ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) and activities of ACC synthase and ACC oxidase in resistant biotypes were less than the susceptible biotype, and were negatively correlated with quinclorac resistance levels, suggesting that inhibition of ethylene biosynthesis was positively correlated with resistance levels., Conclusion: Considering the resistance-dependent inhibition in the ethylene biosynthetic pathway, the mechanisms of resistance to quinclorac in E. crusgalli var. zelayensis involved alteration(s) in the ethylene response pathway, consisting of at least alteration in induction of the enzymes activity of ACC synthase and ACC oxidase., (© 2013 Society of Chemical Industry.)

Background: Studies were carried out to elucidate the mechanism of resistance to ALS-inhibiting herbicides in 29 Echinochloa accessions from water-seeded rice fields of northern Greece and to discriminate the Echinochloa species., Results: Two E. oryzicola accessions were found to be cross-resistant to penoxsulam, bispyribac-sodium, imazamox, foramsulfuron, nicosulfuron and rimsulfuron, whereas all accessions were susceptible (S) to profoxydim. Sequencing of the ALS gene revealed that resistant (R) accessions had a Trp574Leu mutation, which was also confirmed by TspRI endonuclease digestion. Use of cpDNA sequence comparison analysis of Echinochloa species discriminated successfully E. crus-galli and E. oryzicola accessions., Conclusion: This is the first report of Echinochloa oryzicola cross-resistance to ALS-inhibiting herbicides as a result of Trp574Leu mutation. The cpDNA sequence comparison analysis is a reliable tool for discrimination of conventionally classified E. crus-galli and E. oryzicola accessions., (© 2012 Society of Chemical Industry.)

Background: Target-site resistance is the major cause of herbicide resistance to acetolactate synthase (ALS)- and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides in arable weeds, whereas non-target-site resistance is rarely reported. In the Echinochloa phyllopogon biotypes resistant to these herbicides, target-site resistance has not been reported, and non-target-site resistance is assumed to be the basis for resistance. To explore why target-site resistance had not occurred, the target-site genes for these herbicides were isolated from E. phyllopogon, and their expression levels in a resistant biotype were determined., Results: Two complete ALS genes and the carboxyltransferase domain of four ACCase genes were isolated. The expression levels of ALS and ACCase genes were higher in organs containing metabolically active meristems, except for ACC4, which was not expressed in any organ. The differential expression among examined organs was more prominent for ALS2 and ACC2 and less evident for ALS1, ACC1 and ACC3., Conclusion: E. phyllopogon has multiple copies of the ALS and ACCase genes, and different expression patterns were observed among the copies. The existence of three active ACCase genes and the difference in their relative expression levels could influence the occurrence of target-site resistance to ACCase inhibitors in E. phyllopogon., (Copyright © 2012 Society of Chemical Industry.)

Background: Bifora radians, an annual weed in winter wheat, is distributed mainly in the Mediterranean area, Asia Minor and the Caucasus. It infests winter-sown crops of the Central Anatolia and Middle Black Sea regions of Turkey. Field experiments in heavily B. radians-infested fields were conducted over 3 years in Samsun, Turkey, to determine the response of B. radians to ALS-inhibiting herbicides, because growers had complained of a decrease in herbicide effect., Results: The efficacy of ALS inhibitors on a putatively tolerant population sprayed annually with ALS inhibitors and an adjacent allegedly sensitive population was estimated at the ED(50) and ED(90) response levels. The recommended rates of herbicides controlled 90% of the weed (ED(90)) in the sensitive population at the early stage of B. radians development, but not in the tolerant population. The relative potencies (ED(x(tolerant))/ED(x(sensitive))) of herbicides on the two populations were estimated by assuming years as being random effects. The relative potency was on average about 1.7, irrespective of the ED(x) levels., Conclusion: Although the relative potencies were not large, they were large enough to be noted by growers. In field experiments it would be important to establish tools demonstrating when farmers recognise loss of herbicide efficacy. There has been no indication of evolution of resistant biotypes so far, but continuous spraying favours biotypes with increased levels of tolerance., (Copyright © 2011 Society of Chemical Industry.)

Background: Quinclorac (3,7-dichloro-quinoline-carboxylic acid) is a selective herbicide widely used to control annual grasses and certain broadleaf weeds. Echinochloa phyllopogon (Stapf) Koss. is the most noxious grass weed in California rice fields and has evolved resistance to multiple herbicides with different modes of action. A quinclorac-resistant (R) E. phyllopogon biotype found in a Sacramento Valley rice field where quinclorac has never been applied was investigated., Results: Resistant to susceptible (S) GR(50) (herbicide rate for 50% growth reduction) ratios ranged from 6 to 17. The cytochrome P450 inhibitor malathion (200 mg L(-1)) caused R plants to become as quinclorac susceptible as S plants. Quinclorac rapidly (6 HAT) stimulated ethylene formation in S plants, but only marginally in R plants. Malathion pretreatment did not reduce ethylene formation by quinclorac-treated S and R plants. Activity of β-cyanoalanine synthase (β-CAS) in tissue extracts was 2-3-fold greater in R than in S plants, and incubation of shoot extracts with 1 mM malathion reduced β-CAS activity by 40% in both biotypes., Conclusion: Resistance to quinclorac in R E. phyllopogon involved at least two mechanisms: (a) insensitivity along the response pathway whereby quinclorac induces ethylene production; (b) enhanced β-CAS activity, which should enable greater HCN detoxification following quinclorac stimulation of ethylene biosynthesis. This unveils new resistance mechanisms for this multiple-resistant biotype widely spread throughout California rice fields., (Copyright © 2011 Society of Chemical Industry.)