Evolution in action: plants resistant to herbicides

Identification of substituted variants of plastoquinone-9 as potent and specific photosynthetic inhibitors in cyanobacteria and plants

The unprenylated benzoquinones 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone), 2-chloro-1,4-benzoquinone (CBQ), 2,6-dimethyl-1,4-benzoquinone (DMBQ), 2,6-dichloro-1,4-benzoquinone (DCBQ), and 2,6-dimethoxy-1,4-benzoquinone (DMOBQ) were tested as putative antimetabolites of plastoquinone-9, a vital electron and proton carrier of oxygenic phototrophs. Duroquinone and CBQ were the most effective at inhibiting the growth of the cyanobacterium Synechocystis sp. PCC 6803 either in photomixotrophic or photoautotrophic conditions. Duroquinone, a close structural analog of the photosynthetic inhibitor methyl-plastoquinone-9, was found to possess genuine bactericidal activity towards Synechocystis at a concentration as low as 10 μM, while at the same concentration CBQ acted only as a mild bacteriostat. In contrast, only duroquinone displayed marked cytotoxicity in axenically-grown Arabidopsis, resulting in damages to photosystem II and hindered net CO2 assimilation. Metabolite profiling targeted to photosynthetic cofactors and pigments indicated that in Arabidopsis duroquinone does not directly inhibit plastoquinone-9 biosynthesis. Taken together, these data indicate that duroquinone offers prospects as an algicide and herbicide.

Unraveling the reasons for failure to control Amaranthus albus: insights into herbicide application at different growth stages, temperature effect, and herbicide resistance on a regional scale

BACKGROUND

This study investigates factors contributing Amaranthus albus control failure in processing tomato fields in northern Israel. The study region is characterized by a significant climate gradient from east to west, providing the opportunity to investigate the effect of critical elements of the agricultural environment, e.g., temperature. Eight populations were collected from commercial fields in this region. Post-emergence herbicide efficacy of metribuzin, a photosystem II inhibitor, and rimsulfuron, an acetolactate synthase (ALS) inhibitor, was assessed through dose-response analyses at various growth stages. Temperature effects on control efficacy and resistance mechanisms were also explored.

RESULTS

Standard metribuzin dose (X) was ineffective on A. albus plants with more than six true-leaves, whereas 2X dose proved effective. Rimsulfuron at 16X dose was ineffective on plants with more than four true-leaves. We report here the first case of target site resistance to ALS inhibitors in A. albus, due to point mutation in the ALS gene (Pro197 to Leu). Furthermore, our findings suggest potential involvement of CYT P450 enzymes in enhanced metabolizing of rimsulfuron. An overall decrease in dry weight was observed in response to both herbicides at 16/22 °C (P < 0.0001). Rimsulfuron was effective against only one population when applied at 28/34 °C. A possible fitness cost associated with target site-resistant biotypes was observed under low temperature conditions, leading to effective control.

CONCLUSION

This regional-scale study highlights the challenges faced by growers, emphasizes the need for adapting management practices to the local climatic conditions and lays the groundwork for implementing location-specific weed management strategies in commercial fields. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A novel mutation Trp-2027-Gly in acetyl-CoA carboxylase confers resistance to cyhalofop-butyl in Chinese sprangletop (Leptochloa chinensis)

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.

Simulated herbicide mixtures delay both specialist monogenic and generalist polygenic resistance evolution in weeds

BACKGROUND

Evolution of herbicide-resistant weed populations is a major challenge to world food production. Using different herbicides in rotation and/or using different herbicides together as mixtures are strategies that may delay the selection of resistance. This study used simulation modelling to investigate whether mixtures and rotations can delay the selection of both generalist polygenic and specialist monogenic herbicide resistance, and whether these strategies are more likely to lead to the selection of generalist resistance in weed types with varying biological characteristics.

RESULTS

Our simulations suggest that well-designed effective herbicide mixtures should delay evolution of both polygenic and monogenic resistance better than rotations and single herbicides across all weed types. Both mixture and rotation strategies increased the likelihood of polygenic resistance compared to single-herbicide use, and the likelihood of polygenic resistance increased as the fecundity and competitiveness of the weed increased. Whether monogenic or polygenic resistance occurred in each case depended most on the relative initial allele frequencies. We did not find that herbicide mixtures were more likely than rotations to lead to the selection of generalist polygenic resistance. The simulated efficacy of mixtures over rotations decreased if components were used at reduced rates or when individual components had already been used solo.

CONCLUSION

Herbicide rotations and particularly well-designed mixtures should delay evolution of both polygenic and monogenic resistance, especially if used as part of an effective integrated weed management programme. However, herbicide mixtures and rotations may also increase the risk that resistance will be generalist polygenic rather than specialist monogenic. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Confirmation and characterization of the first case of acetolactate synthase (ALS)-inhibitor resistance in Japanese brome (Bromus japonicus) in the US

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.

Cytochrome P450 CYP81A104 in Eleusine indica confers resistance to multiherbicide with different modes of action

BACKGROUND

Developing herbicide-resistant (HR) crop cultivars is an efficient way to control weeds and minimize crop yield losses. However, widespread and long-term herbicide application has led to the evolution of resistant weeds. Here, we established a resistant (R) E. indica population, collected from imidazolinone-resistant rice cultivar fields.

RESULTS

The R population evolved 4.5-fold resistance to imazamox. Acetolactate synthase (ALS) gene sequencing and ALS activity assays excluded the effect of target-site resistance in this population. P450 inhibitor malathion pretreatment significantly reversed resistance to imazamox. RNA sequencing showed that a P450 gene CYP81A104 was expressed higher in R versus susceptible (S) plants. Arabidopsis overexpressing CYP81A104 showed resistance to ALS inhibitors (imazamox, tribenuron-methyl, penoxsulam and flucarbazone-sodium), PSII inhibitor (bentazone), hydroxyphenyl pyruvate dioxygenase inhibitor (mesotrione) and auxin mimics (MCPA), which was generally consistent with the results presented in the R population.

CONCLUSION

This study confirmed that the CYP81A104 gene endowed resistance to multiherbicides with different modes-of-action. Our findings provide an insight into the molecular characteristics of resistance and contribute to formulating an appropriate strategy for weed management in HR crops. © 2024 Society of Chemical Industry.

Comparative genome-wide analysis of circular RNAs in Brassica napus L.: target-site versus non-target-site resistance to herbicide stress

Circular RNAs (circRNAs), a class of non-coding RNA molecules, are recognized for their unique functions; however, their responses to herbicide stress in Brassica napus remain unclear. In this study, the role of circRNAs in response to herbicide treatment was investigated in two rapeseed cultivars: MH33, which confers non-target-site resistance (NTSR), and EM28, which exhibits target-site resistance (TSR). The genome-wide circRNA profiles of herbicide-stressed and non-stressed seedlings were analyzed. The findings indicate that NTSR seedlings exhibited a greater abundance of circRNAs, shorter lengths of circRNAs and their parent genes, and more diverse functions of parent genes compared with TSR seedlings. Compared to normal-growth plants, the herbicide-stressed group exhibited similar trends in the number of circRNAs, functions of parent genes, and differentially expressed circRNAs as observed in NTSR seedlings. In addition, a greater number of circRNAs that function as competing microRNA (miRNA) sponges were identified in the herbicide stress and NTSR groups compared to the normal-growth and TSR groups, respectively. The differentially expressed circRNAs were validated by qPCR. The differntially expressed circRNA-miRNA networks were predicted, and the mRNAs targeted by these miRNAs were annotated. Our results suggest that circRNAs play a crucial role in responding to herbicide stress, exhibiting distinct responses between NTSR and TSR in rapeseed. These findings offer valuable insights into the mechanisms underlying herbicide resistance in rapeseed.

Early silique-shedding wild radish (Raphanus raphanistrum L.) phenotypes persist in a long-term harvest weed seed control managed field in Western Australia

BACKGROUND

This study introduces a wild radish population collected from Yelbeni in the Western Australian grainbelt that evolved an early silique abscission (shedding) trait to persist despite long-term harvest weed seed control (HWSC) use. In 2017, field-collected seed (known herein as Yelbeni) was compared to surrounding ruderal and field-collected populations in a fully randomized common garden study.

RESULTS

The Yelbeni population exhibited a higher rate of silique abscission when compared to the ruderal populations collected from the site before wheat (Triticum aestivum L.) harvest (assessed at soft dough stage, Zadoks 83). A similar common garden study was conducted in the subsequent season (2018) using progeny reproduced on a single site without stress. The HWSC-selected progeny (Yelbeni P) shed 1048 (±288) siliques before wheat maturity at the soft dough stage (Zadoks 83) compared to 25 (±7) siliques from the pooled control populations. The Yelbeni P population only flowered 6 days earlier (FT50 as determined by log-logistic analysis) than pooled control populations, which is unlikely to fully account for the increased rate of silique abscission. The Yelbeni P population also located its lowest siliques below the lowest height for harvest interception (10 cm), which is likely to increase HWSC evasion. The mechanism inducing early silique-shedding is yet to be determined; however, wild radish is known for its significant genetic variability and has demonstrated its capacity to adapt to environmental and management stresses.

CONCLUSION

This study demonstrates that the repeated use of HWSC can lead to the selection of HWSC-avoidance traits including early silique-shedding before harvest and/or locating siliques below the harvest cutting height for interception. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Metabolism-Based Herbicide Resistance to Mesosulfuron-methyl and Identification of Candidate Genes in Bromus japonicus

The evolved resistance of Bromus japonicus Houtt. to ALS-inhibiting herbicides is well established. Previous studies have primarily focused on target-site resistance; however, non-target-site resistance has not been well characterized. This investigation demonstrated that ALS gene sequencing did not detect any previously known resistance mutations in a mesosulfuron-methyl-resistant (MR) population, and notably, treatment with the P450 monooxygenase (P450) inhibitor malathion markedly heightened susceptibility to mesosulfuron-methyl. Utilizing UPLC-MS/MS analysis confirmed elevated mesosulfuron-methyl metabolism in MR plants. The integration of Isoform Sequencing (Iso-Seq) and RNA Sequencing (RNA-Seq) facilitated the identification of candidate genes associated with non-target sites in a subpopulation with two generations of herbicide selection. Through qRT-PCR analysis, 21 differentially expressed genes were characterized, and among these, 10 genes (comprising three P450s, two glutathione S-transferases, one glycosyltransferase, two ATP-binding cassette transporters, one oxidase, and one hydrolase) exhibited constitutive upregulation in resistant plants. Our findings substantiated that increased herbicide metabolism is a driving force behind mesosulfuron-methyl resistance in this B. japonicus population.

Phenanthrene-Induced Cytochrome P450 Genes and Phenanthrene Tolerance Associated with Arabidopsis thaliana CYP75B1 Gene

Polycyclic aromatic hydrocarbons (PAHs) form an important group of organic pollutants due to their distribution in the environment and their carcinogenic and/or mutagenic effects. In order to identify at the molecular level some of the players in the biodegradation and tolerance response to PAHs in plants, we have phenotyped 32 Arabidopsis thaliana T-DNA mutant lines corresponding to 16 cytochrome P450 (CYP) genes that showed to be differentially expressed under contrasted stress conditions induced by phenanthrene, a 3-ring PAH. This screening has allowed us to identify CYP75B1 (At5g07990) T-DNA mutants as the only ones being sensitive to phenanthrene-induced stress, supporting that CYP75B1 protein is necessary for PAH tolerance. CYP75B1 codes for a 3'flavonol hydroxylase. CYP75B1 gene was heterologously expressed on yeast in order to investigate whether it affects the A. thaliana response to phenanthrene by participating in its metabolization. Heterologously-produced CYP75B1 enzyme shows to be catalytically efficient against its physiological substrates (e.g., naringenin) but unable to metabolize phenanthrene or 9-phenanthrenol. In contrast, CYP75B1 seems rather involved in phenanthrene tolerance as a crucial element by regulating concentration of antioxidants through the production of 3'-hydroxylated flavonoids such as quercetin and cyanidin. In particular, we report a highly increased generation of reactive oxygen species (H2O2 and singlet oxygen) in cyp75b1 mutants compared to control plants in response to phenanthrene treatment. Overall, CYP75B1 shows to play an important role in the response to the deleterious effects of phenanthrene exposure and this is related to oxidative stress sensitivity rather than metabolization.

First case of evolved herbicide resistance in the holoparasite sunflower broomrape, Orobanche cumana Wallr

The development and commercialisation of sunflower varieties tolerant to acetolactate synthase (ALS)-inhibiting herbicides some 20 years ago provided farmers with an alternative method for the cost-effective control of Orobanche cumana. In 2020, however, two independent sunflower broomrape populations from Drama (GR-DRA) and Orestiada (GR-ORE), Greece, were reported to be heavily infested with O. cumana after application of the ALS-inhibiting herbicide imazamox. Here we have investigated the race of GR-DRA and GR-ORE and determined the basis of resistance to imazamox in the two Greek O. cumana samples. Using a set of five diagnostic sunflower varieties characterised by different resistant genes with respect to O. cumana infestation, we have clearly established that the GR-ORE and GR-DRA populations belong to the invasive broomrape races G and G+, respectively. Live underground tubercles and emerged shoots were identified at the recommended field rate of imazamox for GR-DRA and GR-ORE but not for two other standard sensitive populations in a whole plant dose response test using two different herbicide-tolerant sunflower hybrids as hosts. Sequencing of the ALS gene identified an alanine 205 to aspartate mutation in all GR-ORE samples. Most GR-DRA tubercles were characterised by a second serine 653 to asparagine ALS mutation whilst a few GR-DRA individuals contained the A205D mutation. Mutations at ALS codons 205 and 653 are known to impact on the binding and efficacy of imazamox and other imidazolinone herbicides. The knowledge generated here will be important for tracking and managing broomrape resistance to ALS-inhibiting herbicides in sunflower growing regions.

RNA and protein biomarkers for detecting enhanced metabolic resistance to herbicides mesosulfuron-methyl and fenoxaprop-ethyl in black-grass (Alopecurus myosuroides)

BACKGROUND

The evolution of non-target site resistance (NTSR) to herbicides leads to a significant reduction in herbicide control of agricultural weed species. Detecting NTSR in weed populations prior to herbicide treatment would provide valuable information for effective weed control. While not all NTSR mechanisms have been fully identified, enhanced metabolic resistance (EMR) is one of the better studied, conferring tolerance through increased herbicide detoxification. Confirming EMR towards specific herbicides conventionally involves detecting metabolites of the active herbicide molecule in planta, but this approach is time-consuming and requires access to well-equipped laboratories.

RESULTS

In this study, we explored the potential of using molecular biomarkers to detect EMR before herbicide treatment in black-grass (Alopecurus myosuroides). We tested the reliability of selected biomarkers to predict EMR and survival after herbicide treatments in both reference and 27 field-derived black-grass populations collected from sites across the UK. The combined analysis of the constitutive expression of biomarkers and metabolism studies confirmed three proteins, namely, AmGSTF1, AmGSTU2 and AmOPR1, as differential biomarkers of EMR toward the herbicides fenoxaprop-ethyl and mesosulfuron in black-grass.

CONCLUSION

Our findings demonstrate that there is potential to use molecular biomarkers to detect EMR toward specific herbicides in black-grass without reference to metabolism analysis. However, biomarker development must include testing at both transcript and protein levels in order to be reliable indicators of resistance. This work is a first step towards more robust resistance biomarker development, which could be expanded into other herbicide chemistries for on-farm testing and monitoring EMR in uncharacterised black-grass populations. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Differential Resistance to Acetyl-CoA Carboxylase Inhibitors in Rice: Insights from Two Distinct Target-Site Mutations

Weeds present a significant challenge to agricultural productivity, and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides have proven to be effective in managing weed populations in rice fields. To develop ACCase-inhibiting herbicide-resistant rice, we generated mutants of rice ACCase (OsACC) featuring Ile-1792-Leu or Gly-2107-Ser substitutions through ethyl methyl sulfonate (EMS) mutagenesis. The Ile-1792-Leu mutant displayed cross-resistance to aryloxyphenoxypropionate (APP) and phenylpyrazoline (DEN) herbicides, whereas the Gly-2107-Ser mutants primarily exhibited cross-resistance to APP herbicides with diminished resistance to the DEN herbicide. In vitro assays of the OsACC activity revealed an increase in resistance to haloxyfop and quizalofop, ranging from 4.84- to 29-fold in the mutants compared to that in wild-type. Structural modeling revealed that both mutations likely reduce the binding affinity between OsACC and ACCase inhibitors, thereby imparting resistance. This study offers insights into two target-site mutations, contributing to the breeding of herbicide-resistant rice and presenting alternative weed management strategies in rice cultivation.

Current status of community resources and priorities for weed genomics research

Weeds are attractive models for basic and applied research due to their impacts on agricultural systems and capacity to swiftly adapt in response to anthropogenic selection pressures. Currently, a lack of genomic information precludes research to elucidate the genetic basis of rapid adaptation for important traits like herbicide resistance and stress tolerance and the effect of evolutionary mechanisms on wild populations. The International Weed Genomics Consortium is a collaborative group of scientists focused on developing genomic resources to impact research into sustainable, effective weed control methods and to provide insights about stress tolerance and adaptation to assist crop breeding.

Pro197Ser and the new Trp574Leu mutations together with enhanced metabolism contribute to cross-resistance to ALS inhibiting herbicides in Sinapis alba

White mustard, (Sinapis alba), a problematic broadleaf weed in many Mediterranean countries in arable fields has been detected as resistant to tribenuron-methyl in Tunisia. Greenhouse and laboratory studies were conducted to characterize Target-Site Resistance (TSR) and the Non-Target Site Resistance (NTSR) mechanisms in two suspected white mustard biotypes. Herbicide dose-response experiments confirmed that the two S. alba biotypes were resistant to four dissimilar acetolactate synthase (ALS)-pinhibiting herbicide chemistries indicating the presence of cross-resistance mechanisms. The highest resistance factor (>144) was attributed to tribenuron-methyl herbicide and both R populations survived up to 64-fold the recommended field dose (18.7 g ai ha-1). In this study, the metabolism experiments with malathion (a cytochrome P450 inhibitor) showed that malathion reduced resistance to tribenuron-methyl and imazamox in both populations, indicating that P450 may be involved in the resistance. Sequence analysis of the ALS gene detected target site mutations in the two R biotypes, with amino acid substitutions Trp574Leu, the first report for the species, and Pro197Ser. Molecular docking analysis showed that ALSPro197Ser enzyme cannot properly bind to tribenuron-methyl's aromatic ring due to a reduction in the number of hydrogen bonds, while imazamox can still bind. However, Trp574Leu can weaken the binding affinity between the mutated ALS enzyme and both herbicides with the loss of crucial interactions. This investigation provides substantial evidence for the risk of evolving multiple resistance in S. alba to auxin herbicides while deciphering the TSR and NTSR mechanisms conferring cross resistance to ALS inhibitors.

Target-site and non-target-site resistance mechanisms confer mesosulfuron-methyl resistance in Alopecurus aequalis

BACKGROUND

Shortawn foxtail (Alopecurus aequalis Sobol.) is a noxious weed in China. The resistance of A. aequalis developed rapidly due to the long-term application of acetolactate synthase (ALS)-inhibiting herbicides. Here, a suspected mesosulfuron-methyl-resistant A. aequalis population, Aa-R, was collected from a wheat field in China.

RESULTS

A dose‒response test showed that the Aa-R population has evolved a high level of resistance to mesosulfuron-methyl, and its growth was suppressed by imazamox, pyroxsulam and bispyribac-sodium. ALS gene sequence analysis revealed that a known resistance-related mutation (Pro-197-Thr) was present in the Aa-R population. Moreover, ALS gene overexpression was detected in the Aa-R population. The mesosulfuron-methyl resistance could be reversed by cytochrome P450 monooxygenase (CYP450) and glutathione S-transferase (GST) inhibitors. In addition, enhanced metabolism of mesosulfuron-methyl was detected in the Aa-R population compared with the susceptible population. NADPH-cytochrome P450 reductase and GST activities were strongly inducible in the Aa-R population. One CYP450 gene, CYP74A2, and one GST gene, GST4, were constitutively upregulated in the Aa-R population. Molecular docking results showed the binding affinity of CYP74A2 and GST4 for the tested ALS-inhibiting herbicides, respectively.

CONCLUSION

This study confirmed that target-site resistance and non-target-site resistance involving CYP450 and GST were the main mechanisms involved in resistance in the mesosulfuron-methyl-resistant A. aequalis population.

Assessing the predictability of fungicide resistance evolution through in vitro selection

Plant pathogens are highly adaptable, and have evolved to overcome control measures including multiple classes of fungicides. More effective management requires a thorough understanding of the evolutionary drivers leading to resistance. Experimental evolution can be used to investigate evolutionary processes over a compressed timescale. For fungicide resistance, applications include predicting resistance ahead of its emergence in the field, testing potential outcomes under multiple different fungicide usage scenarios or comparing resistance management strategies. This review considers different experimental approaches to in vitro selection, and their suitability for addressing different questions relating to fungicide resistance. When aiming to predict the evolution of new variants, mutational supply is especially important. When assessing the relative fitness of different variants under fungicide selection, growth conditions such as temperature may affect the results as well as fungicide choice and dose. Other considerations include population size, transfer interval, competition between genotypes and pathogen reproductive mode. However, resistance evolution in field populations has proven to be less repeatable for some fungicide classes than others. Therefore, even with optimal experimental design, in some cases the most accurate prediction from experimental evolution may be that the exact evolutionary trajectory of resistance will be unpredictable.

Weed biology and management in the multi-omics era: Progress and perspectives

Weeds pose a significant threat to crop production, resulting in substantial yield reduction. In addition, they possess robust weedy traits that enable them to survive in extreme environments and evade human control. In recent years, the application of multi-omics biotechnologies has helped to reveal the molecular mechanisms underlying these weedy traits. In this review, we systematically describe diverse applications of multi-omics platforms for characterizing key aspects of weed biology, including the origins of weed species, weed classification, and the underlying genetic and molecular bases of important weedy traits such as crop-weed interactions, adaptability to different environments, photoperiodic flowering responses, and herbicide resistance. In addition, we discuss limitations to the application of multi-omics techniques in weed science, particularly compared with their extensive use in model plants and crops. In this regard, we provide a forward-looking perspective on the future application of multi-omics technologies to weed science research. These powerful tools hold great promise for comprehensively and efficiently unraveling the intricate molecular genetic mechanisms that underlie weedy traits. The resulting advances will facilitate the development of sustainable and highly effective weed management strategies, promoting greener practices in agriculture.

The Cys-2088-Arg mutation in the ACCase gene and enhanced metabolism confer cyhalofop-butyl resistance in Chinese sprangletop (Leptochloa chinensis)

Acetyl-CoA carboxylase (ACCase)-inhibiting herbicides are among the most commonly used herbicides to control grassy weeds, especially Leptochloa chinensis, in rice fields across China. Herein, we collected a suspected resistant (R) population of L. chinensis (HFLJ16) from Lujiang county in Anhui Province. Whole plant dose response tests showed that, compared with the susceptible (S) population, the R population showed high resistance to cyhalofop-butyl (22-fold) and displayed cross-resistance to metamifop (9.7-fold), fenoxaprop-P-ethyl (18.7-fold), quizalofop-P-ethyl (7.6-fold), clodinafop-propargyl (12-fold) and clethodim (8.4-fold). We detected an amino acid substitution (Cys-2088-Arg) in the ACCase of resistant L. chinensis. However, ACCase gene expression levels were not significantly different (P > 0.05) between R plants and S plants, without or with cyhalofop-butyl treatment. Furthermore, pretreatment with piperonyl butoxide (PBO, a cytochrome P450 monooxygenase (CYP450) inhibitor) or 4-chloro-7-nitrobenzoxadiazole (NBD-Cl, a glutathione-S-transferase (GST) inhibitor), inhibited the resistance of the R population to cyhalofop-butyl significantly (by approximately 60% and 26%, respectively). Liquid chromatography tandem mass spectrometry analysis showed that R plants metabolized cyhalofop-butyl and cyhalofop acid (its metabolite) significantly faster than S plants. Three CYP450 genes, one GST gene, and two ABC transporter genes were induced by cyhalofop-butyl and were overexpressed in the R population. Overall, GST-associated detoxification, CYP450 enhancement, and target-site gene mutation are responsible for the resistance of L. chinensis to cyhalofop-butyl.

Target-site mutations Ile1781Leu and Ile2041Asn in the ACCase2 gene confer resistance to fluazifop-p-butyl and pinoxaden herbicides in a johnsongrass accession from Arkansas, USA

Johnsongrass [Sorghum halepense (L.) Pers.] is a troublesome weed species in different agricultural and non-agricultural areas. Because of its biology, reproductive system, and seed production, effective management is challenging. An accession with low susceptibility to the acetyl-CoA carboxylase (ACCase)-inhibiting herbicides fluazifop-p-butyl (fluazifop) and pinoxaden was collected in eastern Arkansas. In this research, the molecular mechanisms responsible for ACCase resistance were investigated. Dose-response experiments showed a resistance factor of 181 and 133 for fluazifop and pinoxaden, respectively. Molecular analysis of both ACCase1 and ACCase2 genes was researched. Nucleotide comparison of ACCase1 between resistant and susceptible accessions showed no single nucleotide polymorphisms. Nonetheless, analysis of ACCase2 in fluazifop-resistant johnsongrass plants revealed the Ile1781Leu target-site mutation was dominant (nearly 75%), whereas the majority of pinoxaden-resistant johnsongrass plants had the Ile2041Asn (60%). Not all sequenced johnsongrass plants displayed a target-site mutation, suggesting the presence of additional resistance mechanisms. Amplification of ACCase1 and ACCase2 was not responsible for resistance because of the similar values obtained in both resistant and susceptible accessions. Experiments with malathion and NBD-Cl suggest the presence of herbicide metabolism. Outcomes of this research demonstrated that fluazifop- and pinoxaden-resistant johnsongrass plants displayed a target-site mutation in ACCase2, but also that non-target-site resistance mechanisms would be involved and require a detailed study.

The Pro-197-Thr mutation in the ALS gene confers novel resistance patterns to ALS-inhibiting herbicides in Bromus japonicus in China

Introduction

Bromus japonicus is one of the most notorious agricultural weeds in China. The long-term use of ALS-inhibiting herbicides has led to rapid evolution of herbicide resistance in B. japonicus. B. japonicus population (BJ-R) surviving mesosulfuron-methyl treatment was collected from wheatland. Here, we aimed to confirm the resistance mechanisms in this putative resistant population.

Methods

The dose-reponse tests were used to test the resistance level of the B. japonicus to ALS-inhibiting herbicides. Pretreatment with P450 and GST inhibitors and GST activity assays were used to determine whether P450 or GST was involved in the resistance of the BJ-R population. Sanger sequencing was used to analyse the ALS mutation of the BJ-R population. RT-qPCR was used to confirm the the expression levels of the ALS gene in mesosulfuron-methyl -resistant (BJ-R) and-susceptible (BJ-S) B. japonicus. An in vitro ALS activity assay was used to determine the ALS activity of the BJ-R and BJ-S populations. Homology modelling and docking were used to determine the binding energy of the BJ-R and BJ-S populations with ALS-inhibiting herbicides.

Results

B. japonicus population (BJ-R) was confirmed to be 454- and 2.7-fold resistant to the SU herbicides mesosulfuron-methyl and nicosulfuron, and 7.3-, 2.3-, 1.1- and 10.8-fold resistant to the IMI herbicide imazamox, the TP herbicide penoxsulam, the PTB herbicide pyribenzoxim and the SCT herbicide flucarbazone-sodium, respectively, compared with its susceptible counterpart (BJ-S). Neither a P450 inhibitor nor a GST inhibitor could reverse the level of resistance to mesosulfuron-methyl in BJ-R. In addition, no significant differences in GST activity were found between the BJ-R and BJ-S. ALS gene sequencing revealed a Pro-197-Thr mutation in BJ-R, and the gene expression had no significant differences between the BJ-R and BJ-S. The ALS activity of BJ-R was 106-fold more tolerant to mesosulfuron-methyl than that of BJ-S. Molecular docking showed that the binding energy of the ALS active site and mesosulfuron-methyl was changed from -6.67 to -4.57 kcal mol-1 due to the mutation at position 197.

Discussion

These results suggested that the Pro-197-Thr mutation was the main reason for the high resistance level of BJ-R to mesosulfuron-methyl. Unlike previous reports of the cross-resistance pattern conferred by this mutation, we firstly documented that the Pro-197-Thr mutation confers broad cross-resistance spectrums to ALS-inhibiting herbicides in B. japonicus.

Genomic characterisation and dissection of the onset of resistance to acetyl CoA carboxylase-inhibiting herbicides in a large collection of Digitaria insularis from Brazil

An in-depth genotypic characterisation of a diverse collection of Digitaria insularis was undertaken to explore the neutral genetic variation across the natural expansion range of this weed species in Brazil. With the exception of Minas Gerais, populations from all other states showed high estimates of expected heterozygosity (HE > 0.60) and genetic diversity. There was a lack of population structure based on geographic origin and a low population differentiation between populations across the landscape as evidenced by average Fst value of 0.02. On combining haloxyfop [acetyl CoA carboxylase (ACCase)-inhibiting herbicide] efficacy data with neutral genetic variation, we found evidence of presence of two scenarios of resistance evolution in this weed species. Whilst populations originating from north-eastern region demonstrated an active role of gene flow, populations from the mid-western region displayed multiple, independent resistance evolution as the major evolutionary mechanism. A target-site mutation (Trp2027Cys) in the ACCase gene, observed in less than 1% of resistant populations, could not explain the reduced sensitivity of 15% of the populations to haloxyfop. The genetic architecture of resistance to ACCase-inhibiting herbicides was dissected using a genome wide association study (GWAS) approach. GWAS revealed association of three SNPs with reduced sensitivity to haloxyfop and clethodim. In silico analysis of these SNPs revealed important non-target site genes belonging to families involved in herbicide detoxification, including UDPGT91C1 and GT2, and genes involved in vacuolar sequestration-based degradation pathway. Exploration of five genomic prediction models revealed that the highest prediction power (≥0.80) was achieved with the models Bayes A and RKHS, incorporating SNPs with additive effects and epistatic interactions, respectively.

Insight into the herbicide resistance patterns in Lolium rigidum populations in Tunisian and Moroccan wheat regions

Rigid ryegrass (Lolium rigidum Gaud.) is one of the most troublesome weeds in Moroccan and Tunisian cereal crop fields. In total, 19 rigid ryegrass field populations were randomly selected in northern wheat crop areas of Morocco and Tunisia to examine the patterns of herbicide resistance to acetolactate synthase (ALS)- and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. Greenhouse experiments confirmed reduced sensitivity to ALS- and/or ACCase-inhibiting herbicides in all L. rigidum populations. The occurrence of target-site resistance (TSR) was tested using high-throughput genotyping. The advent of next-generation sequencing (NGS) has enabled easy identification of causal mutations and confirmed the presence of ALS and ACCase mutations at specific codons conferring TSR. Thirteen populations showed resistance to ALS-inhibiting herbicides associated with point mutations in positions Pro-197-Thr, Pro-197-Ser, Pro-197-Leu, Pro-197-Gln and Trp-574-Leu, while resistance to ACCase-inhibiting herbicides was detected in 18 populations in positions Asp-2078-Val, Trp-2027-Cys, Ile-1781-Leu, Gly-2096-Ala, and Ile-2041-Asn of the enzymes conferring TSR. Additionally, dose-response experiments with pyroxsulam applied after the inhibition of cytochrome P450 monooxygenase by malathion showed an increase in sensitivity in two out of seven highly resistant (HR) rigid ryegrass populations. This demonstrates the presence of non-target-site resistance (NTSR) in some ryegrass populations. Further evidence of NTSR was investigated in dose-response experiments with pyroxsulam, following pretreatment with the glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl), which partially reversed resistance in only a few individuals of two L. rigidum populations. Hence, our study confirms the existence of multiple and cross-resistance to ALS- and ACCase-inhibiting herbicides in L. rigidum from Morocco and Tunisia with both TSR and NTSR mechanisms. These results emphasize local resistance management as an important tool to detect and mitigate gene flow from rigid ryegrass populations where resistance has evolved.

Intergenerational consequences of an auxin-like herbicide on plant sensitivity to a graminicide mediated by a fungal endophyte

In agroecosystems, herbicides are the predominant anthropogenic selection pressure for agriculture weed species. While weeds are the primary target, herbicides can have adverse impacts on non-target plant beneficial microorganisms. We aimed to investigate the influence of a foliar endophytic fungus (Epichloë occultans) on the sensitivity of Lolium multiflorum to a graminicide herbicide (diclofop-methyl) during both plant ontogeny and progeny. Susceptible individuals to diclofop-methyl with and without endophyte were pre-exposed to the auxin 2,4-D herbicide. This herbicide is known to stimulate the metabolic detoxification mechanism (CYP-450) of diclofop-methyl. Regardless of the endophyte, 2,4-D pre-treatment increased mother plant survival to nearly 100 % under diclofop treatment but not in the progeny. Furthermore, maternal plant exposure to 2,4-D reduced endophyte transmission to the seeds and from seed-to-seedlings. Our findings suggest that, despite a reduction in diclofop-methyl sensitivity during the ontogeny of mother plants, 2,4-D-mediated induction of likely CYP-450 metabolism is not intergenerationally transmitted and shows detrimental effects on the symbiotic endophyte persistence.

Action of the fungal compound citrinin, a bioherbicide candidate, on photosystem II

BACKGROUND

Bioherbicides are becoming more attractive as safe weed control tools towards sustainable agriculture. Natural products constitute an important source chemicals and chemical leads for discovery and development of novel pesticide target sites. Citrinin is a bioactive compound produced by fungi of the genera Penicillium and Aspergillus. However, its physiological-biochemical mechanism as a phytotoxin remains unclear.

RESULTS

Citrinin causes visible leaf lesions on Ageratina adenophora similar to those produced by the commercial herbicide bromoxynil. Phytotoxicity bioassay tests using 24 plant species confirmed that citrinin has a broad activity spectrum and therefore has potential as a bioherbicide. Based on chlorophyll fluorescence studies, citrinin mainly blocks PSII electron flow beyond plastoquinone QA at the acceptor side, resulting in the inactivation of PSII reaction centers. Furthermore, molecular modeling of citrinin docking to the A. adenophora D1 protein suggests that it binds to the plastoquinone QB site by a hydrogen bond between the O1 hydroxy oxygen atom of citrinin and the histidine 215 of the D1 protein, the same way as classical phenolic PSII herbicides do. Finally, 32 new citrinin derivatives were designed and sorted according to free energies on the basis of the molecular model of an interaction between the citrinin molecule and the D1 protein. Five of the modeled compounds had much higher ligand binding affinity within the D1 protein compared with lead compound citrinin.

CONCLUSION

Citrinin is a novel natural PSII inhibitor that has the potential to be developed into a bioherbicide or utilized as a lead compound for discovery of new derivatives with high herbicidal potency. © 2023 Society of Chemical Industry.

Trp-574-Leu mutation and metabolic resistance by cytochrome P450 gene conferred high resistance to ALS-inhibiting herbicides in Descurainia sophia

Descurainia sophia (flixweed) is a troublesome weed in winter wheat fields in North China. Resistant D. sophia populations with different acetolactate synthetase (ALS) mutations have been reported in recent years. In addition, metabolic resistance to ALS-inhibiting herbicides has also been identified. In this study, we collected and purified two resistant D. sophia populations (R1 and R2), which were collected from winter wheat fields where tribenuron-methyl provided no control of D. sophia at 30 g a.i. ha-1. Whole plant bioassay and ALS activity assay results showed the R1 and R2 populations had evolved high-level resistance to tribenuron-methyl and florasulam and cross-resistance to imazethapyr and pyrithiobac‑sodium. The two ALS genes were cloned from the leaves of R1 and R2 populations, ALS1 (2004 bp) and ALS2 (1998 bp). A mutation of Trp 574 to Leu in ALS1 was present in both R1 and R2. ALS1 and ALS2 were cloned from R1 and R2 populations respectively and transferred into Arabidopsis thaliana. Homozygous T3 transgenic seedlings with ALS1 of R1 or R2 were resistant to ALS-inhibiting herbicides and the resistant levels were the same. Transgenic seedlings with ALS2 from R1 or R2 were susceptible to ALS-inhibiting herbicides. Treatment with cytochrome P450 inhibitor malathion decreased the resistant levels to tribenuron-methyl in R1 and R2. RNA-Seq was used to identify target cytochrome P450 genes possibly involved in resistance to ALS-inhibiting herbicides. There were five up-regulated differentially expressed cytochrome P450 genes: CYP72A15, CYP83B1, CYP81D8, CYP72A13 and CYP71A12. Among of them, CYP72A15 had the highest expression level in R1 and R2 populations. The R1 and R2 populations of D. sophia have evolved resistance to ALS-inhibiting herbicides due to Trp 574 Leu mutation in ALS1 and possibly other mechanisms. The resistant function of CYP72A15 needs further research.

Transformative Approaches for Sustainable Weed Management: The Power of Gene Drive and CRISPR-Cas9

Weeds can negatively impact crop yields and the ecosystem's health. While many weed management strategies have been developed and deployed, there is a greater need for the development of sustainable methods for employing integrated weed management. Gene drive systems can be used as one of the approaches to suppress the aggressive growth and reproductive behavior of weeds, although their efficacy is yet to be tested. Their popularity in insect pest management has increased, however, with the advent of CRISPR-Cas9 technology, which provides specificity and precision in editing the target gene. This review focuses on the different types of gene drive systems, including the use of CRISPR-Cas9-based systems and their success stories in pest management, while also exploring their possible applications in weed species. Factors that govern the success of a gene drive system in weeds, including the mode of reproduction, the availability of weed genome databases, and well-established transformation protocols are also discussed. Importantly, the risks associated with the release of weed populations with gene drive-bearing alleles into wild populations are also examined, along with the importance of addressing ecological consequences and ethical concerns.

Mechanism of safener mefenpyr-diethyl biodegradation by a newly isolated Chryseobacterium sp. B6 from wastewater sludge and application in co-contaminated soil

Safener mefenpyr-diethyl (MFD) was applied to cereal crops along with herbicides to improve herbicide selectivity for crops and weeds. However, the degradation mechanism of MFD in the environment remains unclear. One MFD-degrading bacterium, Chryseobacterium sp. B6, was isolated from activated sludge. According to Box-Behnken's optimal design, the degradation efficiency of MFD can reach 92% under conditions of pH 7.5, 30 °C, and a MFD concentration of 184 mg L-1. The degradation half-life experiment showed that a high concentration of MFD (300 mg L-1) inhibited the degradation ability of strain B6. Additionally, strain B6 was resistant to Ba2+, Cr3+, Li+, Zn2+, and Cu2+. The MFD degradation products of strain B6 were detected by GC/MS and its degradation pathway was proposed. MFD was first hydrolyzed by a hydrolase to an intermediate (RS)-1-(2,4-dichlorophenyl)-5-methyl-2-pyrazoline-5-carboxylic acid ethyl ester-3-carboxylic acid, and then further degraded by a decarboxylase to form the intermediate (RS)-1-(2,4-dichlorophenyl)-5-methyl-2-pyrazoline-5-carboxylic acid ethyl ester, finally, it is completely degraded by strain B6. Furthermore, strain B6 could effectively remove MFD from MFD-contaminated soil, and the half-life of MFD was also significantly reduced in MFD and Cu2+ co-contaminated soil after inoculating strain B6. To our knowledge, strain B6 was the first strain reported to degrade safener MFD, and this study provides a valuable candidate to remediate the co-contaminated soil with MFD and Cu2+.

Enhanced metabolic resistance mechanism endows resistance to metamifop in Echinochloa crus-galli (L.) P. Beauv

Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.), one of the worst weeds in paddy fields in China, has been frequently reported evolving resistance to acetyl-CoA carboxylase (ACCase) inhibiting herbicides. However, in the previous research, more attention was paid to target-site resistance (TSR) mechanisms, the non-target-site resistance (NTSR) mechanisms have not been well-established. In this study, the potential mechanism of resistance in a metamifop-resistant E. crus-galli collected from Kunshan city, Jiangsu Province, China was investigated. Dose-response assays showed that the phenotypic resistant population (JS-R) has evolved 4.3-fold resistance to metamifop compared with the phenotypic susceptible population (YN-S). The ACCase CT gene sequencing and relative ACCase gene expression levels studies showed that no mutations were detected in the ACCase CT gene in both YN-S and JS-R, and there was no significant difference in the relative ACCase gene expression between YN-S and JS-R. After the pre-processing of glutathione-S-transferase (GSTs) inhibitor NBD-Cl, the resistance level of JS-R to metamifop was reversed 18.73%. Furthermore, the GSTs activity of JS-R plants was significantly enhanced compared to that of YN-S plants. UPLC-MS/MS revealed that JS-R plants had faster metabolic rates to metamifop than YN-S plants. Meanwhile, the JS-R popultion exhibited resistant to cyhalofop-butyl and penoxsulam. In summary, this study presented a novel discovery regarding the global emergence of metabolic resistance to metamifop in E. crus-galli. The low-level resistance observed in the JS-R population was not found to be related to TSR but rather appeared to be primarily associated with the overexpression of genes in the GSTs metabolic enzyme superfamily.

Yeast of Eden: microbial resistance to glyphosate from a yeast perspective

First marketed as RoundUp, glyphosate is history's most popular herbicide because of its low acute toxicity to metazoans and broad-spectrum effectiveness across plant species. The development of glyphosate-resistant crops has led to increased glyphosate use and consequences from the use of glyphosate-based herbicides (GBH). Glyphosate has entered the food supply, spurred glyphosate-resistant weeds, and exposed non-target organisms to glyphosate. Glyphosate targets EPSPS/AroA/Aro1 (orthologs across plants, bacteria, and fungi), the rate-limiting step in the production of aromatic amino acids from the shikimate pathway. Metazoans lacking this pathway are spared from acute toxicity and acquire their aromatic amino acids from their diet. However, glyphosate resistance is increasing in non-target organisms. Mutations and natural genetic variation discovered in Saccharomyces cerevisiae illustrate similar types of glyphosate resistance mechanisms in fungi, plants, and bacteria, in addition to known resistance mechanisms such as mutations in Aro1 that block glyphosate binding (target-site resistance (TSR)) and mutations in efflux drug transporters non-target-site resistance (NTSR). Recently, genetic variation and mutations in an amino transporter affecting glyphosate resistance have uncovered potential off-target effects of glyphosate in fungi and bacteria. While glyphosate is a glycine analog, it is transported into cells using an aspartic/glutamic acid (D/E) transporter. The size, shape, and charge distribution of glyphosate closely resembles D/E, and, therefore, glyphosate is a D/E amino acid mimic. The mitochondria use D/E in several pathways and mRNA-encoding mitochondrial proteins are differentially expressed during glyphosate exposure. Mutants downstream of Aro1 are not only sensitive to glyphosate but also a broad range of other chemicals that cannot be rescued by exogenous supplementation of aromatic amino acids. Glyphosate also decreases the pH when unbuffered and many studies do not consider the differences in pH that affect toxicity and resistance mechanisms.

Repeated evolution of herbicide resistance in Lolium multiflorum revealed by haplotype-resolved analysis of acetyl-CoA carboxylase

Herbicide resistance in weeds is one of the greatest challenges in modern food production. The grass species Lolium multiflorum is an excellent model species to investigate evolution under similar selection pressure because populations have repeatedly evolved resistance to many herbicides, utilizing a multitude of mechanisms to neutralize herbicide damage. In this work, we investigated the gene that encodes acetyl-CoA carboxylase (ACCase), the target site of the most successful herbicide group available for grass weed control. We sampled L. multiflorum populations from agricultural fields with history of intense herbicide use, and studied their response to three ACCase-inhibiting herbicides. To elucidate the mechanisms of herbicide resistance and the genetic relationship among populations, we resolved the haplotypes of 97 resistant and susceptible individuals by sequencing ACCase amplicons using long-read DNA sequencing technologies. Our dose-response data indicated the existence of many, often unpredictable, resistance patterns to ACCase-inhibiting herbicides, where populations exhibited as much as 37-fold reduction in herbicide response. The majority of the populations exhibited resistance to all three herbicides studied. Phylogenetic and molecular genetic analyses revealed multiple evolutionary origins of resistance-endowing ACCase haplotypes, as well as widespread admixture in the region regardless of cropping system. The amplicons generated were diverse, with haplotypes exhibiting 26-110 polymorphisms. Polymorphisms included insertions and deletions 1-31 bp in length, none of which were associated with the resistance phenotype based on an association analysis. We also found evidence that some populations have multiple mechanisms of resistance. Our results highlight the astounding genetic diversity in L. multiflorum populations, and the potential for repeated evolution of herbicide resistance across the landscape that challenges weed management approaches and jeopardizes sustainable weed control practices. We provide an in-depth discussion of the evolutionary and practical implications of our results.

The herbicide bensulfuron-methyl inhibits rice seedling development by blocking calcium ion flux in the OsCNGC12 channel

Identification of translocator protein-related genes involved in bensulfuron-methyl (BSM) uptake and transport in rice could facilitate the development of herbicide-tolerant cultivars by inactivating them. This study found that the OsCNGC12 mutants not only reduced BSM uptake but also compromised the Ca2 ⁺ efflux caused by BSM in the roots, regulating dynamic equilibrium of Ca2 ⁺ inside the cell and conferring non-target-site tolerance to BSM.

A glutathione S-transferase and a cytochrome P450 may confer cyhalofop-butyl resistance in Leptochloa chinensis (L.) Nees

BACKGROUND

Leptochloa chinensis (L.) Nees is a troublesome weed across China in rice fields, and a suspected L. chinensis resistant population (R) that has survived the recommended field dose of cyhalofop-butyl was collected in a rice field of Hunan Province, China. In this study, we aimed to determine the acetyl-CoA carboxylase-inhibiting herbicide resistance profile of this R population and to investigate its mechanisms of resistance to cyhalofop-butyl.

RESULTS

Compared with the susceptible population (S), the R population was confirmed to be 18.9-, 3.2-, 4.1-, 3.6- and 5.8- fold resistant to the APP herbicides cyhalofop-butyl, haloxyfop-P-methyl, clodinafop-propargyl, metamifop and fenoxaprop-P-ethyl, respectively. ACCase gene sequencing analysis revealed no known resistance mutations for TSR in the R population. Pretreatment with the glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) and cytochrome P450 (CYP450) inhibitor malathion reversed resistance to cyhalofop-butyl. The GST gene GSTU1 and CYP450 gene CYP707A5 were constitutively upregulated in the R population according to RNA-seq analysis and RT-qPCR verification. The molecular docking results indicated a good affinity of the active site for five APP herbicides with GSTU1 and CYP707A5.

CONCLUSION

This study shows that the GSTU1 and CYP707A5 genes expressed highly in the R population may be responsible for cyhalofop-butyl resistance in L. chinensis.

Directed evolution rice genes with randomly multiplexed sgRNAs assembly of base editors

CRISPR-based directed evolution is an effective breeding biotechnology to improve agronomic traits in plants. However, its gene diversification is still limited using individual single guide RNA. We described here a multiplexed orthogonal base editor (MoBE), and a randomly multiplexed sgRNAs assembly strategy to maximize gene diversification. MoBE could induce efficiently orthogonal ABE (<36.6%), CBE (<36.0%), and A&CBE (<37.6%) on different targets, while the sgRNA assembling strategy randomized base editing events on various targets. With respective 130 and 84 targets from each strand of the 34th exon of rice acetyl-coenzyme A carboxylase (OsACC), we observed the target-scaffold combination types up to 27 294 in randomly dual and randomly triple sgRNA libraries. We further performed directed evolution of OsACC using MoBE and randomly dual sgRNA libraries in rice, and obtained single or linked mutations of stronger herbicide resistance. These strategies are useful for in situ directed evolution of functional genes and may accelerate trait improvement in rice.

Current status of cyhalofop-butyl and metamifop resistance and diversity of the ACCase gene mutations in Chinese sprangletop (Leptochloa chinensis) from China

Leptochloa chinensis populations in China have evolved widespread resistance to acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides cyhalofop-butyl (CyB) and metamifop (Met). 124 L. chinensis populations, randomly collected from rice fields in Jiangsu Province, were surveyed for CyB and Met resistance status, and all potential ACCase gene resistance-conferring mutations and effective pre-emergence herbicides for its control were investigated. Single-dose tests confirmed that 82 (66.1%) and 70 (56.4%) populations evolved resistance to CyB and Met, respectively. ACCase sequencing revealed that 56.4% of the populations contain plants with diverse target-site ACCase mutations (Ile1781Leu, Trp1999Cys, Trp2027Cys, Trp2027Ser, Ile2041Asn, Gly2096Ala, and in particular, a Leu1818Phe mutation). Notably, the Leu1818Phe mutation had been detected in 8 resistant populations, indicating this mutation was prone to occur in L. chinensis. Additionally, 9.7% of the populations may have single metabolic resistance to CyB, as these populations was susceptible to Met, and no any ACCase mutations were found. Moreover, the resistant populations with different ACCase mutations showed 6.5 to 33.6-fold resistance to CyB, and 4.4 to 82.6-fold resistance to Met. Importantly, five pre-emergence herbicides, including pretilachlor, pendimethalin, clomazone, pyraclonil, and mefenacet, all exhibited good control effect on resistant L. chinensis populations. This work confirmed the prevalence and distribution of CyB and Met resistance in L. chinensis. Target-site ACCase mutations made a major contribution to CyB and Met resistance. Pre-emergence herbicides could be valuable tools for management of resistant L. chinensis populations.

Target gene mutations endowed cross-resistance to acetolactate synthase-inhibiting herbicides in wild Brassica juncea

Wild Brassica juncea is a troublesome weed that infests wheat fields in China. Two suspected wild B. juncea populations (19-5 and 19-6) resistant to acetolactate synthase (ALS) inhibitors were collected from wheat fields in China. To clarify their resistance profiles and resistance mechanism, the resistance levels of populations 19-5 and 19-6 to ALS-inhibiting herbicides and their underlying target-site resistance mechanism were investigated. The results showed that the 19-5 population exhibited resistance to tribenuron-methyl, pyrithiobac‑sodium and florasulam, while the 19-6 population was resistant to tribenuron-methyl, pyrithiobac‑sodium, imazethapyr and florasulam. Using the homologous cloning method, two ALS genes were identified in wild B. juncea, with one gene (ALS1) encoding 652 amino acids and the other (ALS2) encoding 655 amino acids. Pro-197-Arg mutation on ALS2 and Trp-574-Leu mutation on ALS1, together with the combination of these two mutations in a single plant, were observed in both 19-5 and 19-6 populations. ALS2 enzymes carrying the Pro-197-Arg mutation were cross-resistant to tribenuron-methyl, pyrithiobac‑sodium, imazerthapyr and florasulam, with resistance index (RI) values of 6.23, 32.81, 7.97 and 1162.50, respectively. Similarly, ALS1 enzymes with Trp-574-leu substitutions also displayed high resistance to these four herbicides (RI values ranging from 132.61 to 3375.00). In addition, the combination of Pro-197-Arg (ALS2) and Trp-574-Leu (ALS1) mutations increased the resistance level of the ALS enzyme to ALS inhibitors, with its RI values 3.83-214.19, 6.88-37.34, 1.91-31.82 and 2.03-5.90-fold higher than a single mutation for tribenuron-methyl, pyrithiobac‑sodium, imazerthapyr and florasulam, respectively. Collectively, Pro-197-Arg mutation on ALS2, Trp-574-Leu mutation on ALS1 and the combination of Pro-197-Arg (ALS2) and Trp-574-Leu (ALS1) mutations in wild B. juncea could endow broad-spectrum resistance to ALS inhibitors, which might provide guides for establishing effective strategies to prevent or delay such resistance evolution in this weed.

First Report on Resistance to HPPD Herbicides Mediated by Nontarget-Site Mechanisms in the Grass Leptochloa chinensis

The emergence of 4-hydroxyphenylpyruvate dioxygenase (HPPD) herbicides as efficacious target-site herbicides has been noteworthy. In recent years, only four species of broadleaf weeds have developed resistance due to the long-term widespread use of HPPD herbicides. This study represents the first reported instance of a grass weed exhibiting resistance to HPPD inhibitors. We identified a new HPPD-resistant Chinese sprangletop [Leptochloa chinensis (L.) Nees] population (R population). At the recommended dose of tripyrasulfone, the inhibition rate of the R population was only half that of the sensitive population (S). The mechanism underlying resistance does not involve target-site resistance triggered by amino acid mutations or depend on disparities within the HPPD INHIBITOR SENSITIVE 1 (HIS1) gene. The impetus for resistance appears to be interlinked with the metabolic activities of cytochrome P450 monooxygenase (P450) and glutathione S-transferase (GST) family genes. Following RNA sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR) validation, the study suggests that five P450 genes, CYP71C1, CYP74A2, CYP72A1, CYP84A1, and CYP714C2, alongside a single GST gene GSTF1, may be implicated in the process of metabolic detoxification.

Target-Site and Metabolic Resistance Mechanisms to Penoxsulam in Late Watergrass (Echinochloa phyllopogon) in China

Echinochloa phyllopogon, a malignant weed in Northeast China's paddy fields, is currently presenting escalating resistance concerns. Our study centered on the HJHL-715 E. phyllopogon population, which showed heightened resistance to penoxsulam, through a whole-plant bioassay. Pretreatment with a P450 inhibitor malathion significantly increased penoxsulam sensitivity in resistant plants. In order to determine the resistance mechanism of the resistant population, we purified the resistant population from individual plants and isolated target-site resistance (TSR) and nontarget-site resistance (NTSR) materials. Pro-197-Thr and Trp-574-Leu mutations in acetolactate synthase (ALS) 1 and ALS2 of the resistant population drove reduced sensitivity of penoxsulam to the target-site ALS, the primary resistance mechanisms. To fully understand the NTSR mechanism, NTSR materials were investigated by using RNA-sequencing (RNA-seq) combined with a reference genome. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis further supported the enhanced penoxsulam metabolism in NTSR materials. Gene expression data and quantitative reverse transcription polymerase chain reaction (qRT-PCR) validation confirmed 29 overexpressed genes under penoxsulam treatment, with 16 genes concurrently upregulated with quinclorac and metamifop treatment. Overall, our study confirmed coexisting TSR and NTSR mechanisms in E. phyllopogon's resistance to ALS inhibitors.

ALS gene overexpression and enhanced metabolism conferring Digitaria sanguinalis resistance to nicosulfuron in China

Crabgrass (Digitaria sanguinalis) is a common malignant weed in corn fields in China. Recently, the acetolactate synthase (ALS) inhibitor, nicosulfuron, has shown decreasing efficacy against crabgrass. In order to elucidate the molecular basis of resistance to nicosulfuron in crabgrass, we conducted bioassays, combined with gene sequence analysis, relative expression and relative copy number analysis, to characterize resistance in crabgrass populations collected from Beijing, Heilongjiang, Jilin and Anhui provinces. Whole-plant dose-response results indicated that only population collected in Heilongjiang province (HLJ) had developed low level of resistance to nicosulfuron compared with the sensitive population (SD22). No known resistant mutation of ALS gene was found in HLJ population. The real-time fluorescence quantitative PCR results showed that the ALS gene copy number did not differ significantly between the HLJ and SD22 populations. However, the ALS gene expression in the HLJ was 2.07-fold higher than that of the SD22 population at 24 h after treatment with nicosulfuron. Pretreatment with the cytochrome P450 (CYP450) inhibitor malathion, piperonyl butoxide (PBO), and the glutathione S-transferase (GST) inhibitor 4-Chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl) all partially reversed HLJ resistance. Among them, the synergistic effect of PBO and nicosulfuron is the most significant. This is the first report of resistance to nicosulfuron in crabgrass through ALS gene overexpression and possible metabolic resistance.

CRISPR-mediated acceleration of wheat improvement: advances and perspectives

Common wheat (Triticum aestivum) is one of the most widely cultivated and consumed crops globally. In the face of limited arable land and climate changes, it is a great challenge to maintain current and increase future wheat production. Enhancing agronomic traits in wheat by introducing mutations across all three homoeologous copies of each gene has proven to be a difficult task due to its large genome with high repetition. However, clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease (Cas) genome editing technologies offer a powerful means of precisely manipulating the genomes of crop species, thereby opening up new possibilities for biotechnology and breeding. In this review, we first focus on the development and optimization of the current CRISPR-based genome editing tools in wheat, emphasizing recent breakthroughs in precise and multiplex genome editing. We then describe the general procedure of wheat genome editing and highlight different methods to deliver the genome editing reagents into wheat cells. Furthermore, we summarize the recent applications and advancements of CRISPR/Cas technologies for wheat improvement. Lastly, we discuss the remaining challenges specific to wheat genome editing and its future prospects.

Identification of haemanthamine as a phytotoxic alkaloid in Narcissus pseudonarcissus L. (Daffodil) emerging buds

Emerging buds of Narcissus pseudonarcissus were found to accumulate the alkaloid haemanthamine (1) at high concentrations, exceeding that of narciclasine (2), the most abundant constituent in bulbs of the plant. A phytoactivity screening assay demonstrated the novel phytotoxicity of haemanthamine against Raphanus sativus (radish), Lactuca sativus (lettuce), Triticum aestivum (red wheat), Solanum lycopersicum (tomato), Cucumis sativus (cucumber), Ipomoea (Morning glory), and Lens culinaris (lentil). Haemanthamine (1) phytotoxicity was found to exceed that of the commercial herbicide glyphosate and less toxic than narciclasine (2).

Split complementation of base editors to minimize off-target edits

Base editors (BEs) empower the efficient installation of beneficial or corrective point mutations in crop and human genomes. However, conventional BEs can induce unpredictable guide RNA (gRNA)-independent off-target edits in the genome and transcriptome due to spurious activities of BE-enclosing deaminases, and current improvements mostly rely on deaminase-specific mutagenesis or exogenous regulators. Here we developed a split deaminase for safe editing (SAFE) system applicable to BEs containing distinct cytidine or adenosine deaminases, with no need of external regulators. In SAFE, a BE was properly split at a deaminase domain embedded inside a Cas9 nickase, simultaneously fragmenting and deactivating both the deaminase and the Cas9 nickase. The gRNA-conditioned BE reassembly conferred robust on-target editing in plant, human and yeast cells, while minimizing both gRNA-independent and gRNA-dependent off-target DNA/RNA edits. SAFE also substantially increased product purity by eliminating indels. Altogether, SAFE provides a generalizable solution for BEs to suppress off-target editing and improve on-target performance.

Phytotoxicity alleviation of imazethapyr to non-target plant wheat: active regulation between auxin and DIMBOA

Effectively controlling target organisms while reducing the adverse effects of pesticides on non-target organisms is a crucial scientific inquiry and challenge in pesticide ecotoxicology research. Here, we studied the alleviation of herbicide (R)-imazethapyr [(R)-IM] to non-target plant wheat by active regulation between auxin and secondary metabolite 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazine-3(4H)-one (DIMBOA). We found (R)-IM reduced 32.4% auxin content in wheat leaves and induced 40.7% DIMBOA accumulation compared to the control group, which effortlessly disrupted the balance between wheat growth and defense. Transcriptomic results indicated that restoration of the auxin level in plants promoted the up-regulation of growth-related genes and the accumulation of DIMBOA up-regulated the expression of defense-related genes. Auxin and DIMBOA alleviated herbicide stress primarily through effects in the two directions of wheat growth and defense, respectively. Additionally, as a common precursor of auxin and DIMBOA, indole adopted a combined growth and defense strategy in response to (R)-IM toxicity, i.e., restoring growth development and enhancing the defense system. Future regulation of auxin and DIMBOA levels in plants may be possible through appropriate methods, thus regulating the plant growth-defense balance under herbicide stress. Our insight into the interference mechanism of herbicides to the plant growth-defense system will facilitate the design of improved strategies for herbicide detoxification.

Phylogenetic relatedness can influence cover crop-based weed suppression

Cover crops are plants grown to provide regulating, supporting, and cultural ecosystem services in managed environments. In agricultural systems, weed suppression services from cover crops can be an important tool to promote sustainability as reliance on herbicides and tillage for weed management has caused pollution, biodiversity loss, and human health issues. However, to effectively use weed suppression services from cover crops, farmers must carefully select species that fit within their rotations and suppress their problematic weeds. Understanding how the relatedness between cover crops and weeds affects their interactions will help farmers select cover crops for targeted weed management. The phylogenetic distance between species reflects their relatedness and was studied through a series of field experiments that compared weed suppression in winter and summer cover crops with tilled controls. This study demonstrates that cover crops can reduce up to 99% of weed biomass and alter weed community structure by suppressing phylogenetically related weed species. Results also suggest that cover crop planting season can influence weed community structure since only overwintering treatments affected the phylogenetic distance of weed communities. In an applied context, these results help develop cover crop-based weed management systems, demonstrating that problematic weeds can be managed by selecting phylogenetically related cover crop species. More broadly, this study provides a framework for evaluating weed communities through a phylogenetic perspective, which provides new insight into plant interactions in agriculture.

Eleusine indica Cytochrome P450 and Glutathione S-Transferase Are Linked to High-Level Resistance to Glufosinate

Eleusine indica has become a global nuisance weed and has evolved resistance to glufosinate. The involvement of target-site resistance (TSR) in glufosinate resistance in E. indica has been elucidated, while the role of nontarget-site resistance (NTSR) remains unclear. Here, we identified a glufosinate-resistant (R) population that is highly resistant to glufosinate, with a resistance index of 13.5-fold. Molecular analysis indicated that the resistance mechanism of this R population does not involve TSR. In addition, pretreatment with two known metabolic enzyme inhibitors, the cytochrome P450 (CYP450) inhibitor malathion and the glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl), increased the sensitivity of the R population to glufosinate. The results of subsequent RNA sequencing (RNA-seq) and quantitative real-time PCR (RT-qPCR) suggested that the constitutive overexpression of a GST gene (GSTU3) and three CYP450 genes (CYP94s and CYP71) may play an important role in glufosinate resistance. This study provides new insights into the resistance mechanism of E. indica.

Metabolic pathways modulated by coumarin to inhibit seed germination and early seedling growth in Eleusine indica

Coumarin is an allelochemical that is widely present in the plant kingdom and has great potential for weed control. However, its mechanisms of action remain largely unknown. This study employed metabolomic and transcriptomic analyses along with evaluations of amino acid profiles and related physiological indicators to investigate how coumarin inhibits the germination and seedling growth of Eleusine indica by modifying metabolic pathways. At 72 h of germination at 50 and 100 mg L-1 coumarin, E. indica had lower levels of soluble sugar and activities of amylases and higher levels of starch, O2-, H2O2, auxin (IAA) and abscisic acid (ABA) compared to the control. Metabolomic analysis demonstrated that coumarin treatments had a significant impact on the pathways associated with amino acid metabolism and transport and aminoacyl-tRNA biosynthesis. Exposure to coumarin induced significant alterations in the levels of 19 amino acids, with a decrease in 15 of them, including Met, Leu and γ-aminobutyric acid (GABA). Additionally, transcriptomic analysis showed that coumarin significantly disrupted several essential biological processes, including protein translation, secondary metabolite synthesis, and hormone signal transduction. The decrease in TCA cycle metabolite (cis-aconitate, 2-oxoglutarate, and malate) contents was associated with the suppression of transcription for related enzymes. Our findings indicate that the inhibition of germination and growth in E. indica by coumarin involves the suppression of starch conversion to sugars, modification of the amino acid profile, interference of hormone signalling and the induction of oxidative stress. The TCA cycle appears to be one of the most essential pathways affected by coumarin.

First report of target-site resistance to ACCase-inhibiting herbicides in Bromus tectorum L

BACKGROUND

The prevalent and repeated use of acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides for Bromus tectorum L. control in fine fescue (Festuca L. spp) grown for seed has selected ACCase-resistant B. tectorum populations. The objectives of this study were to (1) evaluate the response of nine B. tectorum populations to the ACCase inhibitors clethodim, sethoxydim, fluazifop-P-butyl, and quizalofop-P-ethyl and the acetolactate synthase (ALS) inhibitor sulfosulfuron and (2) characterize the resistance mechanisms.

RESULTS

Bromus tectorum populations were confirmed to be resistant to the ACCase-inhibiting herbicides tested. The levels of resistance varied among the populations for clethodim (resistance ratio, RR = 5.1-14.5), sethoxydim (RR = 18.7-44.7), fluazifop-P-butyl (RR = 3.1-40.3), and quizalofop-P-ethyl (RR = 14.5-36). Molecular investigations revealed that the mutations Ile2041Thr and Gly2096Ala were the molecular basis of resistance to the ACCase-inhibiting herbicides. The Gly2096Ala mutation resulted in cross-resistance to the aryloxyphenoxypropionate (APP) herbicides fluazifop-P-butyl and quizalofop-P-ethyl, and the cyclohexanedione (CHD) herbicides clethodim, and sethoxydim, whereas Ile2041Thr mutation resulted in resistance only to the two APP herbicides. All B. tectorum populations were susceptible to sulfosulfuron (RR = 0.3-1.7).

CONCLUSIONS

This is the first report of target-site mutations conferring resistance to ACCase-inhibiting herbicides in B. tectorum. The results of this study suggest multiple evolutionary origins of resistance and contribute to understanding the patterns of cross-resistance to ACCase inhibitors associated with different mutations in B. tectorum. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Nontarget-site resistance due to rapid physiological response in 2,4-D resistant Conyza sumatrensis: reduced 2,4-D translocation and auxin-induced gene expression

BACKGROUND

Resistance to 2,4-Dichlorophenoxyacetic acid (2,4-D) has been reported in several weed species since the 1950s; however, a biotype of Conyza sumatrensis showing a novel physiology of the rapid response minutes after herbicide application was reported in 2017. The objective of this research was to investigate the mechanisms of resistance and identify transcripts associated with the rapid physiological response of C. sumatrensis to 2,4-D herbicide.

RESULTS

Differences were found in 2,4-D absorption between the resistant and susceptible biotypes. Herbicide translocation was reduced in the resistant biotype compared to the susceptible. In resistant plants 98.8% of [14 C] 2,4-D was found in the treated leaf, whereas ≈13% translocated to other plant parts in the susceptible biotype at 96 h after treatment. Resistant plants did not metabolize [14 C] 2,4-D and had only intact [14 C] 2,4-D at 96 h after application, whereas susceptible plants metabolized [14 C] 2,4-D into four detected metabolites, consistent with reversible conjugation metabolites found in other 2,4-D sensitive plant species. Pre-treatment with the cytochrome P450 inhibitor malathion did not enhance 2,4-D sensitivity in either biotype. Following treatment with 2,4-D, resistant plants showed increased expression of transcripts within plant defense response and hypersensitivity pathways, whereas both sensitive and resistant plants showed increased expression of auxin-response transcripts.

CONCLUSION

Our results demonstrate that reduced 2,4-D translocation contributes to resistance in the C. sumatrensis biotype. The reduction in 2,4-D transport is likely to be a consequence of the rapid physiological response to 2,4-D in resistant C. sumatrensis. Resistant plants had increased expression of auxin-responsive transcripts, indicating that a target-site mechanism is unlikely. © 2023 Society of Chemical Industry.

Cloning and functional characterization of a tau class glutathione transferase associated with haloxyfop-P-methyl resistance in Digitaria sanguinalis

BACKGROUND

Haloxyfop-P-methyl, an acetyl-CoA carboxylase (ACCase)-inhibiting herbicide, has been extensively used to control grass weeds. Widespread use of haloxyfop-P-methyl in cotton fields in China has led to the development of glutathione transferase (GST)-mediated resistance in Digitaria sanguinalis. An RNA-seq analysis identified DsGSTU1, a tau class glutathione transferase from the D. sanguinalis transcriptome as a potential candidate. Here, we cloned DsGSTU1 from D. sanguinalis young leaf tissues and subsequently characterized DsGSTU1 by a combination of sequence analysis, as well as functional heterologous expression in rice.

RESULTS

The full-length coding DNA sequence (CDS) of DsGSTU1 is 717 bp in length. Higher DsGSTU1 expression was observed in haloxyfop-P-methyl-resistant (HR) D. sanguinalis than in haloxyfop-P-methyl-susceptible (HS) plants. Overexpression of the DsGSTU1 gene was confirmed by transformation into the wild-type (WT) Nipponbare rice with pBWA(V)HS, a recombinant expression vector. GST activity in transgenic rice seedlings was 1.18-1.40-fold higher than the WT rice seedlings before and after haloxyfop-P-methyl treatment, respectively. Additionally, transgenic rice seedlings overexpressing DsGSTU1 were less sensitive to haloxyfop-P-methyl.

CONCLUSION

Our combined findings suggest that DsGSTU1 is involved in metabolic resistance to haloxyfop-P-methyl in D. sanguinalis. A better understanding of the major genes contributing to herbicide-resistant D. sanguinalis facilitates the development of resistance management strategies for this global invasive grass weed. © 2023 Society of Chemical Industry.