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Summary The coevolution of plants and their insect herbivores reflects eco‐evolutionary dynamics at work – ecological interactions influence adaptive traits, which feed back to shape the broader ecological community. However, novel anthropogenic stressors like herbicide, which are strong selective agents, can disrupt these dynamics. Little is known about how the evolution of herbicide resistance may impact plant–herbivore interactions. We performed a common garden field experiment using Ipomoea purpurea (common morning glory) and the herbicide glyphosate (Roundup) to investigate the ecological effects of herbicide exposure on insect herbivory patterns and assess the potential evolutionary consequences. We find that plants treated with glyphosate experienced higher levels of herbivory and altered chewing herbivory damage patterns. Additionally, we found that glyphosate resistance is positively associated with herbivory resistance, and uncovered positive selection for increased glyphosate resistance, suggesting that selection for increased glyphosate resistance has the potential to lead to increased herbivory resistance. Positive selection for glyphosate resistance, coupled with the detection of genetic variation for this trait, suggests there is potential for glyphosate resistance – and herbivory resistance via hitchhiking – to further evolve. Our results show that herbicides cannot just influence, but potentially drive the eco‐evolutionary dynamics of plant–herbivore interactions. [ABSTRACT FROM AUTHOR]

Background: Weed infestation in cotton has been reported to offer severe competition and cause yield reduction to a large extent. Weeding via cultural practices is time consuming, tedious, and expensive due to long duration of cotton crop and regular monsoon rains during cotton production in India. Chemical weed control has been successfully utilized in cotton in the recent past. However, continuous use of similar herbicides leads to resistance in weeds against herbicides. And when sprayed to the field, herbicides not only suppress weeds but leave undesirable residues in the soil that are hazardous to the environment. Therefore, a study was performed at cotton research area at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana during two consecutive kharif seasons (2020 and 2021) to determine the most suitable and sustainable weed management strategy through the integration of chemical and cultural methods. Results: Mulching with rice straw of 7.5 t ha−1 resulted in significantly higher cotton seed yield (3 189 and 3 084 kg ha−1) and better weed control in comparison to no mulch treatments (2 990 and 2904 kg ha−1) in 2020 and 2021, respectively. Among various weed management levels, the significantly lowest cotton seed yield was recorded in untreated control (1 841 and 1 757 kg·ha−1 during 2020 and 2021, respectively) in comparison to other treatments while all other treatments were statistically at par with each other during both years of crop experimentation. Conclusion: Mulching with rice straw of 7.5 t·ha−1 along with a pre-emergence application of pendimethalin (active ingredient) at 1.5 kg·ha−1fb (followed by) one hoeings at 45 days after sowing (DAS) and fb glyphosate 2 kg·ha−1 (Shielded spray) at 90 DAS is a viable option for effective control of grassy and broadleaved weeds in Bt cotton in north-west India. [ABSTRACT FROM AUTHOR]

Crop resistance to herbicides is crucial for agricultural productivity and sustainability amidst escalating challenges of weed resistance. Uncovering herbicide resistant genes is particularly important for rice production. In this study, we tested the resistance to three commonly used herbicides: glufosinate, glyphosate and mesotrione of 421 diverse rice cultivars and employed genome-wide association studies (GWAS) to unravel the genetic underpinnings of resistance to these three herbicides in rice. We discovered that cultivated rice exhibited rich variation in resistance to the three herbicides, and the differences among subpopulations were significant. Six identified associations harboring candidate genes for resistance to these herbicides were significant. Among them, RGlu6 and RGly8 were the major QTL for resistance to glufosinate and glyphosate, respectively. The favorable alleles of RGlu6 and RGly8 were primarily present in japonica cultivars that originated from Europe, highlighting the geographic and genetic diversity of herbicide resistance and emphasizing the localized selection pressures in European rice varieties. Moreover, our findings might suggest that traditional target genes may not contain tolerant alleles in nature, and alternative mechanisms with novel loci associated with resistance may work. By mapping the genes for herbicide resistance, our results may help develop new strategies to combat the dual challenges on effective weed management and herbicide sustainability. [ABSTRACT FROM AUTHOR]

The heavy reliance on herbicides for weed control has led to an increase in resistant weeds in the United States. Robotic weed control is emerging as an alternative technology for removing weeds mechanically using artificial intelligence. We develop an integrated weed ecological and economic dynamic (I‐WEED) model to examine the biophysical and economic drivers of adopting robotic weed management and simulate the optimal timing and intensity of robotic adoption within and across growing seasons. We specify a cohort‐based weed growth model that relates yield damages to effective weed density and treats the susceptibility of weeds to herbicides as a renewable resource that can be regenerated by using mechanical weeding robots, due to a fitness cost that makes resistant weeds less prolific. Compared to myopic weed management which ignores resistance development, forward‐looking management leads to earlier adoption of robots and treating robots as complements instead of substitutes to herbicides. This weed management results in adopting fewer robots, deploying robots on a smaller portion of the land, higher profitability, and lower yield loss in the long run, relative to myopic management. Counterintuitively, myopic management leads to a lower resistance level through its higher robot adoption intensity. We also find that a lower level of initial weed seed resistance and/or a higher fitness cost result in a higher level of resistance because they create incentives for farmers to delay the adoption of robotic weed control. Our analysis shows the importance of jointly considering the interactions between weed ecology and economics in analyzing the incentives and effects of robotic weed management on weed resistance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

BACKGROUND: A 4‐year experiment evaluated the effects of different integrated weed management (IWM) programs on the evolution of a Echinochloa crus‐galli population resistant to acetolactate synthase (ALS) inhibitors in a maize cropping system. The programs included the continued use of ALS inhibitors, mixing them with alternative herbicides, or without ALS‐inhibitors, in all cases under maize monocrop or a biennial crop rotation. RESULTS: IWM programs that relied solely on non‐ALS‐inhibitors usually achieved high control levels across years (> 90%). Additionally, Trp574Leu‐resistant plants became prevalent (> 90%) in programs only using ALS inhibitors, while in the rest the frequency of susceptible plants did not substantially decrease below 40%. Regarding the other monitored grass weeds, Digitaria sanguinalis and Panicum dichotomiflorum were effectively controlled in programs using ALS‐inhibitors without soybean rotation or in programs without ALS‐inhibitors altogether, excepting the program relying on an 4‐hydroxyphenylpyruvate dioxygenase (HPPD)‐inhibitor under maize monocrop for the latter species (0%). CONCLUSION: At the end of the experiment, the only IWM programs that reduced infestation levels were the one without ALS‐inhibitors under soybean rotation, and the one with standard pre‐emergence treatments. These findings highlight the effectiveness of crop rotation and alternative herbicides both pre‐ or post‐emergence in controlling E. crus‐galli. ALS‐inhibitors, while challenged by resistance in E. crus‐galli, remain valuable tools for managing other grass weed species in maize. It is crucial to adapt IWM strategies for herbicide‐resistant E. crus‐galli and other grass weed populations to mitigate the further evolution of resistance. © 2024 Corteva Agriscience. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary Populations of Polypogon fugax have developed resistance to many acetyl‐CoA carboxylase (ACCase)‐inhibiting herbicides. This resistance threats the effectiveness and sustainability of herbicide use. In our previous research, a field P. fugax population exhibited GST‐based metabolic resistance to the widely used ACCase‐inhibiting herbicide quizalofop‐p‐ethyl. Here, in this current study, we identified and characterized two GST genes (named as PfGSTF2 and PfGSTF58) that showed higher expression levels in the resistant than the susceptible population. Transgenic rice calli overexpressing PfGSTF2, but not PfGSTF58, became resistant to quizalofop‐p‐ethyl and haloxyfop‐R‐methyl. This reflects similar cross‐resistance pattern to what was observed in the resistant P. fugax population. Transgenic rice seedlings overexpressing PfGSTF2 also exhibited resistance to quizalofop‐p‐ethyl. In contrast, CRISPR/Cas9 knockout of the orthologue gene in rice seedlings increased their sensitivity to quizalofop‐p‐ethyl. LC–MS analysis of in vitro herbicide metabolism by Escherichia coli‐expressed recombinant PfGSTF2 revealed that quizalofop (but not haloxyfop) was detoxified at the ether bond, generating the GSH‐quizalofop conjugate and a propanoic acid derivative with greatly reduced herbicidal activity. Equally, these two metabolites accumulated at higher levels in the resistant population than the susceptible population. In addition, both recombinant PfGSTF2 and PfGSTF58 can attenuate cytotoxicity by reactive oxygen species (ROS), suggesting a role in plant defence against ROS generated by herbicides. Furthermore, the GST inhibitor (NBD‐Cl) reversed resistance in the resistant population, and PfGSTF2 (but not PfGSTF58) responded to NBD‐Cl inhibition. All these suggest that PfGSTF2 plays a significant role in the evolution of quizalofop resistance through enhanced herbicide metabolism in P. fugax. [ABSTRACT FROM AUTHOR]

Summary The chloroplast genome has considerable potential to enhance crop productivity, but it remains underutilized in breeding because it is difficult to modify. This study elucidates the potential of recently developed chloroplast‐targeted C‐to‐T base editors in facilitating the use of the chloroplast genome for crop breeding. The herbicide metribuzin interferes with photosynthesis by binding to the D1 protein of photosystem II, encoded by the chloroplast genome. Naturally occurring D1 mutants with V219I or A251V substitutions are known to have resistance to some herbicides including metribuzin. Here, using the base editors, we introduced these substitutions and showed that the A251V single mutation and the V219 & A251V double mutations conferred significant metribuzin resistance to Arabidopsis thaliana. The V219I & A251V double mutants exhibited increased metribuzin resistance and grew better than the A251V single mutants. Furthermore, the double mutants grew as well as wild‐type plants in the absence of metribuzin. The single and double mutants, which are a challenge to obtain through traditional mutagenesis and crossbreeding methods, can be relatively easily generated using C‐to‐T base editors. In view of the conservation of V219 and A251 across numerous species, C‐to‐T base editing can potentially confer metribuzin resistance to a wide range of crops. Compared to nuclear genes, chloroplast genes are also less likely to spread into wild populations. Our findings suggest that chloroplast‐targeting C‐to‐T base editors will find many roles in future crop breeding efforts. [ABSTRACT FROM AUTHOR]

Weeds are a major threat to agricultural productivity, leading to significant yield losses. This review critically assesses the potential of nanotechnology in developing nanoherbicides as an effective alternative to traditional weed control methods. The properties and encapsulation techniques of various nanoparticles, including interfacial polymerization, in-situ polymerization, coacervation, and organic encapsulation, are analyzed to demonstrate how these methods enhance herbicide efficiency and specificity. A comprehensive literature review synthesizes recent advancements in organic encapsulation techniques, including liposomes and polymeric nanoparticles, which enhance herbicide efficacy and targeted delivery. The findings indicate that nanotechnology can improve herbicide effectiveness by reducing required doses and minimizing off-target effects, enhancing stability and bioavailability. Key findings suggest that nanoherbicides can achieve targeted delivery and reduce off-target effects and environmental impact. Additionally, the review highlights evidence showing that nano-formulations can mitigate issues related to herbicide resistance by improving the stability and increasing the diversity of soil microbes. Furthermore, this study underscores the necessity for further research into the long-term effects and practical applications of nanoherbicides in diverse agricultural settings. By integrating these innovative techniques, farmers can achieve more sustainable weed control, increasing agricultural productivity while mitigating environmental risks. Future research should prioritize field trials to validate these findings and optimize application methods for diverse cropping systems. [ABSTRACT FROM AUTHOR]

Interspecific hybridization between two different Brassicaceae species, namely Brassica rapa ssp. pekinensis (♀) (AA, 2n = 2x = 20) and genetically modified Brassica napus (♂) (AACC, 2n = 4x = 38), was performed to study the transmission of a herbicide resistance gene from a tetraploid to a diploid Brassica species. Initially, four different GM B. napus lines were used for hybridization with B. rapa via hand pollination. Among the F1 hybrids, the cross involving the B. rapa (♀) × GM B. napus (♂) TG#39 line exhibited the highest recorded crossability index of 14.7 ± 5.7. However, subsequent backcross progenies (BC1, BC2, and BC3) displayed notably lower crossability indices. The F1 plants displayed morphological characteristics more aligned with the male parent B. napus, with significant segregation observed in the BC1 generation upon backcrossing with the recurrent parent B. rapa. By the BC2 and BC3 generations, the progeny stabilized, manifesting traits from both parents to varying degrees. Cytogenetic analysis revealed a substantial reduction in chromosome numbers, particularly in backcrossing progenies. BC1 plants typically exhibited 21–25 chromosomes, while BC2 progenies showed 21–22 chromosomes, and by the BC3 generation, stability was achieved with an average of 20 chromosomes. SSR marker analysis confirmed the progressive reduction of C-genome regions, retaining minimal C-genome-specific bands throughout successive backcrossing. Despite the extensive elimination of C-genome-specific genomic regions, the glyphosate resistance gene from the male parent B. napus was introgressed into BC3 progenies, suggesting that the glyphosate resistance gene located and introgressed in A-chromosome/genome regions of the Brassica plants. [ABSTRACT FROM AUTHOR]

Crop resistance to herbicides is crucial for agricultural productivity and sustainability amidst escalating challenges of weed resistance. Uncovering herbicide resistant genes is particularly important for rice production. In this study, we tested the resistance to three commonly used herbicides: glufosinate, glyphosate and mesotrione of 421 diverse rice cultivars and employed genome-wide association studies (GWAS) to unravel the genetic underpinnings of resistance to these three herbicides in rice. We discovered that cultivated rice exhibited rich variation in resistance to the three herbicides, and the differences among subpopulations were significant. Six identified associations harboring candidate genes for resistance to these herbicides were significant. Among them, RGlu6 and RGly8 were the major QTL for resistance to glufosinate and glyphosate, respectively. The favorable alleles of RGlu6 and RGly8 were primarily present in japonica cultivars that originated from Europe, highlighting the geographic and genetic diversity of herbicide resistance and emphasizing the localized selection pressures in European rice varieties. Moreover, our findings might suggest that traditional target genes may not contain tolerant alleles in nature, and alternative mechanisms with novel loci associated with resistance may work. By mapping the genes for herbicide resistance, our results may help develop new strategies to combat the dual challenges on effective weed management and herbicide sustainability. [ABSTRACT FROM AUTHOR]

Weed science plays a vital role in mitigating the negative impacts of weeds in agriculture and natural ecosystems. However, the field has received criticism for its limited theoretical foundation and excessive focus on phenomenological and narrow scope. Our contention is that weed science needs to integrate more ecological theories to foster a deeper understanding of weed ecology, biology, and management. By embracing theoretical frameworks, weed science can enhance its ability to predict and explain weed dynamics, identify underlying mechanisms, and develop sustainable management strategies. This insight emphasizes the advantages of integrating theoretical approaches and offers practical recommendations to integrate ecological theory effectively into weed science research. [ABSTRACT FROM AUTHOR]

Italian ryegrass (Lolium multiflorum Lam.) is a persistent weed species that poses significant management challenges in key agricultural crops such as wheat, corn, cotton, and soybean. This study investigated the prevalence of resistance to ACCase inhibitor herbicides, specifically diclofop and pinoxaden, among field-collected Italian ryegrass populations. The survey revealed widespread resistance to diclofop and emerging cross-resistance to pinoxaden. To elucidate the physiological mechanism of ACCase herbicide resistance, we investigated mutations in the carboxyl-transferase (CT) domain of the ACCase enzyme, a critical region for herbicide sensitivity. Using dCAPS assays and CT domain sequencing, several known resistance-conferring mutations were detected in diclofop survivors, including I1781L, W2027C, I2041N, D2078G, and C2088R. Additionally, other mutations such as L1701M, E1874A, N1878H, G1946E/Q, V1992D, and E2039D were identified. To understand the functional role of these mutations in herbicide resistance, homology modeling was performed using AutoDock Vina for selected mutation combinations. The computational analysis revealed that all mutations and their combinations resulted in reduced binding affinity with diclofop and pinoxaden compared to the wild-type ACCase CT domain. Computational binding energy predictions indicated that the G1946E mutation and the L1701M + I1781L + E1874A + N1878H combination exhibited the lowest affinities for diclofop and pinoxaden, respectively. This study provides valuable insights into the molecular basis of ACCase inhibitor resistance in Italian ryegrass. However, further research is needed to validate the functional significance of each new substitution and its combinations in conferring herbicide resistance. [ABSTRACT FROM AUTHOR]

Weed infestations pose significant challenges to global crop production, demanding effective and sustainable weed control methods. Traditional approaches, such as chemical herbicides, mechanical tillage, and plastic mulches, are not only associated with environmental concerns but also face challenges like herbicide resistance, soil health, erosion, moisture content, and organic matter depletion. Thermal methods like flaming, streaming, and hot foam distribution are emerging weed control technologies along with directed energy systems of electrical and laser weeding. This paper conducts a comprehensive review of laser weeding technology, comparing it with conventional methods and highlighting its potential environmental benefits. Laser weeding, known for its precision and targeted energy delivery, emerges as a promising alternative to conventional control methods. This review explores various laser weeding platforms, discussing their features, applications, and limitations, with a focus on critical areas for improvement, including dwell time reduction, automated navigation, energy efficiency, affordability, and safety standards. Comparative analyses underscore the advantages of laser weeding, such as reduced environmental impact, minimized soil disturbance, and the potential for sustainable agriculture. This paper concludes by outlining key areas for future research and development to enhance the effectiveness, accessibility, and affordability of laser weeding technology. In summary, laser weeding presents a transformative solution for weed control, aligning with the principles of sustainable and environmentally conscious agriculture, and addressing the limitations of traditional methods. [ABSTRACT FROM AUTHOR]

Annual ryegrass (Lolium rigidum) is a problematic weed in winter crops and fallows in the southeastern cropping region (SCR) of Australia. This weed has evolved resistance to multiple herbicide groups, globally. In Australia, L. rigidum is more prevalent in the western and southern regions than in SCR. To assess the herbicide resistance status of L. rigidum, the response of five L. rigidum populations (collected from the SCR) to glyphosate, glufosinate, paraquat, haloxyfop-P-ethyl, and clethodim is determined using dose–response curves. Three parametric logistic models are used to determine the herbicide dose required to achieve 50% survival (LD50) and 50% growth reduction (GR50). The LD50 values for 50% survival at 28 days after treatment range from 1702 g a.e. ha−1 to 8225 g a.e. ha−1 for glyphosate, 1637 g a.i. ha−1 to 1828 g a.i. ha−1 for glufosinate, 141 g a.i. ha−1 to 307 g a.i. ha−1 for paraquat, 11 g a.i. ha−1 to 107 g a.i. ha−1 for haloxyfop-P-ethyl, and 17 g a.i. ha−1 to 48 g a.i. ha−1 for clethodim. The resistance factor, based on GR50 value, is highest in the S7 population (2.2 times) for glyphosate, the S11 population (2.3 times) for glufosinate, the S11 population (2.0 time) for paraquat, the S7 population (3.9 times) for haloxyfop-P-ethyl, and the S3 population (3.1 times) for clethodim, compared with the susceptible or less tolerant population. The S11 population is found to be resistant to five tested herbicides, based on resistance factors. Similarly, the S3 population is highly resistant to glyphosate, haloxyfop-P-ethyl, and clethodim compared with the W4 population. These results suggest that L. rigidum populations in the SCR exhibit resistance to multiple herbicide groups at labelled field rates. The findings highlight the necessity of adopting an integrated management approach, including the use of residual herbicides, tank mixing herbicides with different modes of action, and rotating herbicides in conjunction with cultural and mechanical control methods. [ABSTRACT FROM AUTHOR]

The occurrence of control failure after herbicide application suggests the emergence of tolerant D. nuda in sugarcane crops. However, the presence of species within the herbicide-resistant weed community before the selection process can be partially attributed to ecological adaptability. Biological studies of Digitaria spp. in areas without resistance reports are essential to understand the initial characteristics of populations before resistance events. In the present study, the predominance of Digitaria species was evaluated in ten areas of sugarcane cultivation without records of populations resistant to photosystem II-inhibiting herbicides belonging to four mills. First, we determined the sensitivity of Digitaria populations to herbicides. In addition, interspecific competitiveness and growth under nutrient and water availability conditions were determined for each identified species of Digitaria. The survey revealed a predominance of D. horizontalis and D. nuda in populations composed of D. bicornis and D. ciliaris, and all them were susceptible to herbicides. The combinations of competition between species showed no significant differences. D. nuda has a greater increase of aboveground biomass under water availability, which may favor its adaptation in areas with sugarcane straw left on the soil. The predominance of susceptible D. nuda in some populations is primarily due to its biological characteristics and its adaptation to cultivation practices. However, D. nuda plants obtained from the two susceptible populations showed differential responses to diuron, indicating diversity in populations in terms of herbicide response. [ABSTRACT FROM AUTHOR]

Herbicide-resistant weeds threaten contemporary agriculture by reducing crop yields and quality. Monitoring of herbicide-resistant weeds is essential to the development of informed integrated weed management (IWM) strategies. In 2019 and 2020, a randomized-stratified preharvest survey of 419 fields in Saskatchewan, Canada, was conducted to determine the distribution, frequency of occurrence, and impact of herbicide-resistant weeds. Mature seeds were collected from uncontrolled weeds in each field. The samples were tested for resistance to acetyl-CoA carboxylase (ACCase) and/or acetolactate synthase (ALS)-inhibiting herbicides using whole-plant bioassays under a controlled-environment. In 2019/2020, herbicide-resistant weeds occupied 72% of the surveyed fields, corresponding to an estimated 6.2 million ha of annual cropland and a total field area of 11.4 million ha. Herbicide-resistant weeds cost Saskatchewan farmers an estimated $343 million CAD annually in reduced crop yields and quality, and increased weed control expenditures. Wild oat (Avena fatua L.) had the greatest impact among grass weeds, with ACCase inhibitor resistance documented in 77% and ALS inhibitor resistance in 30% of fields where the weed seeds were collected and tested (47% and 18% of all fields surveyed, respectively). Multiple herbicide (ACCase and ALS inhibitor)-resistant wild oat were documented in 26% of the tested fields. Kochia (Bassia scoparia (L.) A.J. Scott) had the greatest impact among broadleaf weeds, where 100% of the samples tested were ALS inhibitor-resistant (39% of all fields surveyed). The growing prevalence of herbicide-resistant weeds in Saskatchewan warrants further adoption of IWM where non-chemical tactics play an important role in stewardship of the remaining effective herbicides. [ABSTRACT FROM AUTHOR]

The evolution and spread of herbicide resistance among the weed community has increased interest in alternative weed management strategies such as harvest weed seed control. Western Canadian producers have begun adopting physical impact mills as an additional weed management strategy. A survey of early adopters of physical impact mill technology in Canada was conducted to better understand the motivations behind producers adopting, initial experiences, and research needs. Ten producers responded to the survey, accounting for 18 out of an estimated 30 impact mills in use in Canada, believed to be located primarily in the Canadian Prairies. These producers were mainly from larger farms (>4000 ha), equipped the majority of their combines (75% average) and used the mills in essentially all crops grown. The majority of respondents were located in Saskatchewan, with two mills being used in Alberta. Wild oat (Avena fatua L.) (60%) and kochia (Bassia scoparia (L.) A.J. Scott) (50%) were the weeds most frequently mentioned as specific motivators of impact mill adoption. Average increased fuel cost from the mill was estimated at CAD$3.46 ha−1, with average annual maintenance costs of about $1500 per impact mill. Producers relied on information from mill companies and other early-adopting farmers primarily, followed by extension talks and social media. Research needs were also identified by producers that could inform the future direction of harvest weed seed control research in Canada. Future research should focus on confirming efficacy, optimizing combine settings, and looking at integrated systems with precision agriculture technologies. [ABSTRACT FROM AUTHOR]

The transformation protocol based on the dual selection approach (fluorescent protein and herbicide resistance) has been applied here to produce transgenic plants of two cereal species, emmer wheat and bread wheat, with the goal of activating the synthesis of the stress hormone jasmonates by overexpressing ALLENE OXIDE SYNTHASE from Arabidopsis thaliana (AtAOS) and bread wheat (TaAOS) and OXOPHYTODIENOATE REDUCTASE 3 from A. thaliana (AtOPR3) under the strong constitutive promoter (ZmUbi1), either individually or both genes simultaneously. The delivery of the expression cassette encoding AOS was found to affect morphogenesis in both wheat species negatively. The effect of transgene expression on the accumulation of individual jasmonates in hexaploid and tetraploid wheat was observed. Among the introduced genes, overexpression of TaAOS was the most successful in increasing stress-inducible phytohormone levels in transgenic plants, resulting in higher accumulations of JA and JA-Ile in emmer wheat and 12-OPDA in bread wheat. In general, overexpression of AOS, alone or together with AtOPR3, negatively affected leaf lamina length and grain numbers per spike in both wheat species. Double (AtAOS + AtOPR3) transgenic wheat plants were characterized by significantly reduced plant height and seed numbers, especially in emmer wheat, where several primary plants failed to produce seeds. [ABSTRACT FROM AUTHOR]

An increasing number of herbicide‐resistant weeds challenge farming systems worldwide. Bans on active ingredients in chemical crop protection, which result in fewer weed control options, emphasise the importance of herbicide resistance management in arable farming. Resistance testing allows farmers to get an objective overview of the prevailing herbicide resistances on their land and to adjust their management strategies accordingly. Nevertheless, no study has examined farmers' adoption of herbicide resistance tests. For this purpose, an online survey with 197 German arable farmers was conducted. The adoption decision was investigated by applying the theory of planned behaviour framework. The results suggest that informing farmers of the economic benefits associated with herbicide resistance tests can facilitate widespread adoption. Furthermore, awareness of the availability of herbicide resistance tests needs to be raised through both advertising and crop consultants. Results from this study are relevant for several interest groups as the usage of herbicide resistance tests can help reduce the emergence of new resistance by optimising herbicide use at the farm level. [ABSTRACT FROM AUTHOR]

Crop productivity is affected by various abiotic and biotic factors. Weeds act as the most serious biological constraint by reducing crop yield, harbouring insect pests and causing serious health hazards. Chemical herbicides were widely employed for weed control in agricultural fields. However, an increase in herbicide-resistant weeds and rising environmental concerns arising from the overuse of synthetic herbicides have led scientists to explore natural ways of managing weeds that are cost-effective and environment-friendly. Ecological control by allelopathic crops has proved to be of great significance in weed management. This review focuses on the problem of herbicide resistance in weeds and the role of allelochemicals in biological weed control. Additionally, the review includes the discussion on the allelopathic potential of various crop plants for weed control which can be exploited for the development of cost-effective and environment-friendly bioherbicide. Further, the discussion on retention and biodegrability of the allelochemicals in rhizosphere along with the studies involving genetic mechanisms underlying allelopathy that will direct the future researches for further progress using allelopathy as a potential tool in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Plant macroevolutionary studies leverage the phylogenetic position of non-flowering model systems like the liverwort Marchantia polymorpha to investigate the origin and evolution of key plant processes. To date, most molecular genetic studies in Marchantia rely on hygromycin and/or chlorsulfuron herbicide resistance markers for the selection of stable transformants. Here, we used a sulfonamide-resistant dihydropteroate synthase (DHPS) gene to enable sulfadiazine-based transformation selection in M. polymorpha. We demonstrate the reliability of sulfadiazine selection on its own and in combination with existing hygromycin and chlorsulfuron selection schemes through transgene stacking experiments. The utility of this system is further demonstrated through confocal microscopy of a triple transgenic line carrying fluorescent proteins labelling the plasma membrane, cortical microtubules, and the nucleus. Collectively, our findings and resources broaden the capacity to genetically manipulate the increasingly popular model liverwort M. polymorpha. [ABSTRACT FROM AUTHOR]

AbstractThis study examines weed management in legume crops in Morocco. Faced with the challenges of climate change, financial profitability, and herbicide resistance, farmers are adopting a range of strategies, from plowing to herbicide use to agroecological practices. A survey of 244 farmers was conducted in different regions of Morocco. The results show that crop rotation is the most common weed management practice (81.15%), followed by herbicide use (59.43%) and manual weeding (35.25%). Major challenges include weed diversity (81.16%) and weed control budget constraints (84.84%). Farmers’ observations suggest that larger plots are associated with higher weed frequency, underlining the importance of adjusting herbicide application according to field size. In summary, Moroccan farmers are adopting an integrated approach, combining plowing, crop rotations, and herbicides for effective weed management, while facing complex challenges. It is essential to promote innovative and sustainable farming practices, guided by the results of this study, with an emphasis on developing weed-resistant legume varieties. In addition, raising farmers’ awareness of best practices, including the judicious use of herbicides, is crucial for sustainable agriculture in Morocco. [ABSTRACT FROM AUTHOR]

Amaranthus retroflexus L. is a troublesome dicot weed in crop fields and has developed high resistance to nicosulfuron in China. The objective of this study was to determine the effects of specific resistance mutations (A205V, D376E, W574L, S653T, and S653N) of the acetohydroxy acid synthase enzyme (AHAS) on the resistance of A. retroflexus to nicosulfuron. The resistance mutations in A. retroflexus not only conferred 17.17- to 31.70-fold resistance to nicosulfuron but also greatly decreased AHAS sensitivity and increased AHAS binding affinity to substrate pyruvate, which mechanisms were primarily responsible for the observed A. retroflexus resistance. Molecular docking results indicated that these resistance mutations altered AHAS binding free energy with nicosulfuron. All the resistance mutations showed less sensitivity to feedback inhibition by branched-chain amino acids, but the mutations did not necessarily affect biosynthesis in A. retroflexus. This report to compares the various mutations of ArAHAS in vitro and contributes to understanding herbicide resistance in this field weed. [ABSTRACT FROM AUTHOR]

Simple Summary: Plant invasion represents a significant global ecological challenge, and effective management of invasive species requires robust weed risk assessment systems. These systems predominantly rely on understanding the relationships between life history traits and weed occurrence. In this study, we conducted a survey of native weed communities across 666 field sites in agricultural areas of Yangzhou City, China, covering a longitudinal range of 0.86°, a latitudinal range of 0.84°, and an altitude below 100 m. Our findings reveal that dominant weed species are concentrated within a few families and are associated with higher levels of weediness globally. The key traits of prevalent native weeds include moderate plant height, absence of thorns, non-succulent, erect growth forms or lianas, and adaptability to a range of light conditions, whether mesophytic or xerophytic. Dominant native weeds were frequently annuals, biennials, or perennials with moderate vegetative reproduction abilities and high fertility, possessing seeds of moderate size and fruits without mucilage, conspicuous hairs, thorns, or awns. Additionally, many have developed herbicide resistance. This study is the first to focus on the diversity and life history traits of native weed communities in China, providing valuable insights for refining weed risk assessment and management strategies. Native weeds have a long history of adaptation to local environments. Understanding the relationship between the occurrence of native weeds and their life history traits is crucial for effective weed management and risk assessment of plant invasions. In this study, we surveyed native weed species and their dominance across 666 field sites in agricultural areas of Yangzhou City, China, and each site was 13.3 hectares in area. A total of 287 native weed species were recorded, referring to 63 families, among which 45% were 50–100 cm in plant height and 47% were of an erect life type. In terms of the proportions out of the total native weed occurrence dominance, Poaceae, Compositae, and Fabaceae weeds accounted for 30%, 13%, and 11%; liana and perennials both occupied 32%; and aquatic, hygrophyte, sun plant, and shade plant all occupied < 10%. Additionally, the proportions increased with increasing seed production per plant and with increasing weediness reported worldwide. Native weed groups holding moderate vegetative reproduction abilities, moderate seed sizes, or herbicide resistance showed higher proportions. Moreover, most of the native weeds surveyed were not succulent or thorny plants and did not hold thorns, awns, obvious hairs, or mucilage on their fruits. [ABSTRACT FROM AUTHOR]

This study was conducted in a newly established (2-year-old) almond orchard to investigate the effects of five different mulching materials (woven and nonwoven fabric, black and white polyethylene, almond shell) and flame treatments applied at two different frequencies (FL20 and FL30) on weed control and almond growth compared with those of conventional herbicide (glyphosate) application and weedy control. Thus, this study included nine different treatments. The impacts of these treatments on weed density and coverage were periodically monitored. Additionally, the biomass of the weeds was measured at the end of the season to evaluate the effects of the treatments. Because the almond orchard was not yet in the economic fruit-bearing stage, the effects of the treatments were examined in terms of parameters that characterize almond growth, such as plant height, trunk diameter, shoot length, and shoot thickness. The chlorophyll content and water potential values of the trees were also determined. The results of this two-season study indicated that synthetic mulches provided the best outcomes in terms of weed control and almond growth. No weed emergence was observed throughout the season in any of the synthetic mulch treatments. Although almond shells used as organic mulch were highly effective for blocking sunlight, they failed to prevent the growth of some vigorously growing perennials such as Cynodon dactylon and Sorghum halepense that emerged from gaps. Flame treatments demonstrated rapid and effective results; however, they were less successful against the aforementioned monocot perennial weeds and required frequent repetition because of the lack of residual effects. Glyphosate, an herbicide that is commonly used in conventional orcharding, was applied five times throughout the experiment and proved effective weed management compared with that of the weedy control. However, considering the increasing herbicide resistance, environmental and health issues, and growing interest in organic almond cultivation, synthetic mulch applications have emerged as good options. Despite the initially higher establishment costs, synthetic mulches effectively controlled weeds and reduced water stress, thereby promoting almond tree growth. [ABSTRACT FROM AUTHOR]

Acetochlor, as a commonly used pre‐emergent herbicide, can be toxic to crops and affect production if used improperly. However, the toxic mechanism of acetochlor on plants is not fully understood. The present study used a combination of transcriptomic analysis and physiological measurements to investigate the effects of short‐term (15‐day) exposure to different concentrations of acetochlor (1, 10, 20 mg/kg) on the morphology, physiology, and transcriptional levels of pea seedlings, aiming to elucidate the toxic response and resistance mechanisms in pea seedlings under herbicide stress. The results showed that the toxicity of acetochlor to pea seedlings was dose‐dependent, manifested as dwarfing and stem base browning with increasing concentrations, especially at 10 mg/kg and above. Analysis of the antioxidant system showed that from the 1 mg/kg treatment, malondialdehyde, superoxide dismutase, peroxidase, and glutathione peroxidase in peas increased with increasing concentrations of acetochlor, indicating oxidative damage. Analysis of the glutathione (GSH) metabolism system showed that under 10 mg/kg treatment, the GSH content of pea plants significantly increased, and GSH transferase activity and gene expression were significantly induced, indicating a detoxification response in plants. Transcriptomic analysis showed that after acetochlor treatment, differentially expressed genes in peas were significantly enriched in the phenylpropane metabolic pathway, and the levels of key metabolites (flavonoids and lignin) were increased. In addition, we found that acetochlor‐induced dwarfing of pea seedlings may be related to gibberellin signal transduction. Environ Toxicol Chem 2024;43:2005–2019. © 2024 SETAC [ABSTRACT FROM AUTHOR]

S-metolachlor is a selective pre-emergence herbicide used in dryland. However, it is challenging to employ in paddy fields due to its phytotoxic effects on rice. As a common phytohormone, Gibberellin-3 (GA3) is inferred to have the ability to alleviate herbicide phytotoxicity. This study first quantitatively verified the phytotoxicity of s-metolachlor to rice and then demonstrated the mitigative effect of GA3 on these adverse reactions. Furthermore, a transcriptome of rice seedlings subjected to different treatments was constructed to assemble the reference genes, followed by comparative metabolomics and proteomics analyses. Metabolomics revealed an enrichment of flavonoid metabolites in the group of adding GA3, and these flavonoids can eliminate ROS in plants. Proteomics analysis indicated that differential proteins were enriched in the phenylpropanoid biosynthesis pathway responsible for the synthesis of flavonoids and that the functions of most differential proteins are associated with peroxidase. The proteome, combined with the transcriptome, revealed that the expressions of proteins and genes was related to the POD activity in the group of adding GA3. It was speculated that the elimination of ROS is key to alleviating the stress of s-metolachlor on rice growth. It was inferred that the mechanism of GA3 in alleviating the phytotoxicity of the substance s-metolachlor is by increasing the activity of the POD and influencing the growth of rice seedlings through the restoration of flavonoid synthesis. In this study, we screened GA3 as a safener to alleviate the phytotoxicity of s-metolachlor on rice. On this basis, the mechanism of alleviating phytotoxicity was studied. The application range of s-metolachlor might be expanded, providing a new supplementary method for weed control and herbicide resistance management. [ABSTRACT FROM AUTHOR]

Since the introduction and widespread adoption of chemical herbicides, "weed management" has become almost synonymous with "herbicide management." Over-reliance on herbicides and herbicide-resistant crops has given rise to herbicide resistant weeds. Integrated weed management (IWM) identifies three strategies for weed management— biological-cultural, chemical-technological, mechanical-physical—and recommends combining all three to mitigate herbicide resistance. However, adoption of IWM has stalled, and research to understand the adoption of IWM practices has focused on single stakeholder groups, especially farmers. In contrast, decisions about weed management often occur within a social ecosystem where multiple stakeholder groups co-create knowledge and practices. To more holistically investigate perceptions and decision-making related to herbicide resistant weed management, we conducted 23 in-depth interviews in combination with Q methodology with farmers and public-/private-sector agricultural professionals in the state of Georgia (U.S.). Our investigation focused on the management of an increasingly herbicide resistant weed, Palmer amaranth, which enabled broader conversations about agricultural systems, farmer livelihoods, and sustainability. Factor and thematic analyses allowed us to identify and characterize two distinct typologies: one primarily valued agronomic efficiency and relied upon chemical-technological management practices, while the other valued diversifying weed management strategies as the pathway to agronomic and economic success. Typologies diverged substantially in attitudes toward the three weed management strategies, the role of technology, and systems management generally. These two viewpoints have implications for how we understand underlying stakeholder motivations and choices around weed management strategies, both of which are crucial in promoting and supporting farmer use of diverse, ecologically-sound, weed management strategies. [ABSTRACT FROM AUTHOR]

The value of glyphosate to growers practicing minimum or no‐till farming has been primarily a function of three factors: broad‐spectrum weed control, little to no carryover effect, and cost effectiveness. A 2‐year field study was conducted in 2021 and 2022 at the University of Idaho Research and Extension Centers at Kimberly and Aberdeen, ID, to evaluate the efficacy of alternative pre‐plant burndown herbicide treatments as compared to glyphosate treatment, the industry standard in small grain production systems. Herbicide cost comparison and crop injury observation were also conducted. Most herbicide treatments provided ≥$ \ge $90% control of the predominant weed species at 3 weeks after herbicide application. At least six different herbicide treatments had an equivalent cost to that of glyphosate at $26.50 ha−1. No observable damage from herbicide treatments was observed and crop yield was not affected by the treatments. These factors indicate that there are alternatives to pre‐plant burndown herbicides that are equally effective as glyphosate. With combinations of herbicides, each having a different site of action, weed control can be achieved while simultaneously reducing the risk of herbicide resistance. Core Ideas: Alternatives to glyphosate for pre‐plant weed control would reduce overreliance on glyphosate.Alternative herbicides to glyphosate provided ≥90% control of the predominant weed species.At least six different herbicide treatments were effective and had equivalent costs to glyphosate.No visible crop damage or yield reduction was observed from any of the herbicide treatments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Transgenic, dicamba‐resistant soybean and cotton were developed to enable farmers to combat weeds that had evolved resistance to the herbicide glyphosate. The dramatic increases in dicamba use these crops facilitated have led to serious problems, including the evolution of dicamba‐resistant weeds and widespread damage to susceptible crops and farming communities. Disturbingly, this pattern of dicamba use has unfolded while the total herbicide applied to soybean has nearly doubled since 2006. Without substantive changes to agricultural policy and decision making, the next 'silver‐bullet' agrotechnology will likely be no more than another step on the transgene‐facilitated herbicide treadmill. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

EPSPS is a key gene in the shikimic acid synthesis pathway that has been widely used in breeding crops with herbicide resistance. However, its role in regulating cell elongation is poorly understood. Through the overexpression of EPSPS genes, we generated lines resistant to glyphosate that exhibit an unexpected dwarf phenotype. A representative line, DHR1, exhibits a stable dwarf phenotype throughout its entire growth period. Except for plant height, the other agronomic traits of DHR1 are similar to its transgenic explants ZM24. Paraffin section observations showed that DHR1 internodes are shortened due to reduced elongation and division of the internode cells. Exogenous hormones confirmed that DHR1 is not a classical brassinolide (BR)- or gibberellin (GA)-related dwarfing mutant. Hybridization analysis and fine mapping confirmed that the EPSPS gene is the causal gene for dwarfism, and the phenotype can be inherited in different genotypes. Transcriptome and metabolome analyses showed that genes associated with the phenylpropanoid synthesis pathway are enriched in DHR1 compared with ZM24. Flavonoid metabolites are enriched in DHR1, whereas lignin metabolites are reduced. The enhancement of flavonoids likely results in differential expression of auxin signal pathway genes and alters the auxin response, subsequently affecting cell elongation. This study provides a new strategy for generating dwarfs and will accelerate advancements in light simplification in the cultivation and mechanized harvesting of cotton.

Monochoria vaginalis (Burm. f.) C. Presl is a dominant weed in paddy rice cultivation, significantly threatening productivity and farming sustainability. In Subang, Indonesia, synthetic auxin and acetolactate synthase (ALS) inhibitors are commonly used to control M. vaginalis. However, farmers have currently reported declining efficacy of these herbicides. Therefore, this study aimed to confirm the resistance of M. vaginalis to the early post-emergence application of synthetic auxin and ALS inhibitors. Plant bioassays were conducted using the pot test method to determine resistance level. Herbicides were applied 2 weeks after planting M. vaginalis at 0.25, 0.5, 1.0, 2.0, 4.0, and 8.0 times the recommended dose, and untreated plants as control. Herbicides tested were 2,4-D, bensulfuron-methyl, bispyribac sodium, penoxulam, and sulfentrazone. The results obtained based on resistance index values (RI) showed that M. vaginalis populations from Kediri and Gandasari, Subang, had moderately to high resistance to 2,4-D (RI: 8.15 and 13.0) and bensulfuron-methyl (RI: 205.61 and 21.80). Weed was moderately resistant to bispyribac sodium (RI of Kediri biotype: 8.79) and had low to moderate resistance to penoxulam herbicides (RI: 8.94 and 3.56). In contrast, M. vaginalis-resistant biotypes remained susceptible to sulfentrazone (protoporphyrinogen oxidase/PPO inhibitors) herbicide. A significant increase in GR50 was observed between 28 and 56 days after herbicide application, signifying enhanced regrowth. The resistance of M. vaginalis to synthetic auxin and ALS inhibitors presents the need for farmers to consider alternative herbicides, such as PPO inhibitors, to prevent the development of resistant weeds.

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. [ABSTRACT FROM AUTHOR]

BACKGROUND: Raphanus raphanistrum causes $40 million total revenue losses annually in Western Australia partly due to its historically‐documented ability to evolve herbicide resistance to multiple modes of action. In this study, 376 field‐sampled populations of R. raphanistrum were tested for resistance to 21 herbicides applied at the recommended label rate. Eight treatments were herbicide mixtures with two, three or four modes of action. RESULTS: A total of 7199 individual resistance tests were conducted across 4 years by screening approximately 104 000 individual seeds and seedlings. The mean survival of individuals within a population for all standalone herbicides was 9%, whereas survival was significantly decreased to 3.5% with a herbicide mixture. Some herbicides such as triasulfuron (herbicide Group 2), 2,4‐D (Group 4) or diflufenican (Group 12) were highly impacted by resistance, with frequencies of resistant populations being > 50%. Conversely, there was negligible resistance to glyphosate (Group 9) or protoporphyrinogen oxidase (PPO) inhibitors (tiafenacil, saflufenacil + trifludimoxazin, fomesafen: Group 14), and pre‐emergence herbicides (i.e., atrazine or mesotrione: Groups 5 and 27, respectively) remained largely effective. Binary, ternary or quaternary mixtures of Groups 4, 6, 12 and 27 herbicides reduced the frequency of high‐level resistant populations to 7.1%, 3.8% or 0%, respectively. CONCLUSIONS: The cost‐effective control of R. raphanistrum remains a challenge due to herbicide resistance. Raphanus raphanistrum management relies heavily on herbicide uses not yet compromised by resistance, such as pre‐emergence herbicides (atrazine, fomesafen, mesotrione), glyphosate, and mixtures of two, three or four modes of action including bromoxynil, diflufenican, MCPA, picolinafen, pyrasulfotole and topramezone. Strategies that integrate effective herbicide use patterns, novel modes of action and efficiently‐mechanized non‐chemical weed control options (i.e., seed destructors) can completely constrain the selection of herbicide resistance in this highly adaptable species. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Variable efficacy of the acetohydroxyacid synthase (AHAS) inhibitor herbicide, flumetsulam, against dairy pasture populations of Ranunculus acris, has been attributed to resistance. We compared, over two years, the fitness of two resistant (R) clones and nine susceptible (S) clones treated or not with flumetsulam by measuring seed yields and survival of plants. Without the herbicide, all plants grew and survived. The seed yields of the R and S plants without the herbicide were similar (327 and 217 seeds/plant, respectively in Year 1, and 257 and 323 seeds/plant in Year 2) indicating no fitness penalty to the resistance. With the herbicide, growth and survival of the R plants was unaffected, whereas all S plants were defoliated before seedhead formation but 96% regrew from their rhizomes in Year 2. Seed yields of the treated R and S plants in Year 1 were 347 and 0 seeds/plant, respectively and 243 and 205 seeds/plant in Year 2. Survival of flumetsulam-susceptible R. acris plants following spraying would maintain susceptible AHAS alleles in the population, while without a fitness penalty, resistant plants would persist in non-spraying years facilitating further selection when the herbicide is used again. [ABSTRACT FROM AUTHOR]

Discovering and engineering herbicide-resistant genes is a crucial challenge in crop breeding. This study focuses on the 4-hydroxyphenylpyruvate dioxygenase Inhibitor Sensitive 1-Like (HSL) protein, prevalent in higher plants and exhibiting weak catalytic activity against many β-triketone herbicides (β-THs). The crystal structures of maize HSL1A complexed with β-THs were elucidated, identifying four essential herbicide-binding residues and explaining the weak activity of HSL1A against the herbicides. Utilizing an artificial evolution approach, we developed a series of rice HSL1 mutants targeting the four residues. Then, these mutants were systematically evaluated, identifying the M10 variant as the most effective in modifying β-THs. The initial active conformation of substrate binding in HSL1 was also revealed from these mutants. Furthermore, overexpression of M10 in rice significantly enhanced resistance to β-THs, resulting in a notable 32-fold increase in resistance to methyl-benquitrione. In conclusion, the artificially evolved M10 gene shows great potential for the development of herbicide-resistant crops. [ABSTRACT FROM AUTHOR]

Flixweed (Descurainia sophia) is a weed that seriously affects wheat fields in China. Over the past 20 years, it has evolved resistance to the herbicide tribenuron-methyl. In the present study, a resistant D. sophia population with a Pro-197-Thr mutation of acetolactate synthetase (ALS) was found to have a resistance index of 457.37 for tribenuron-methyl. Under the same growth conditions, the seeds of resistant (R) and susceptible (S) populations exhibited similar vitality but the germination rates of R seeds were higher than those of S seeds. This result demonstrated that seed dormancy periods were shorter in the R seeds. RNA-Seq transcriptome analysis was then used to choose candidate genes that could regulate seed dormancy pathways in the R population. A total of 504,976,046 clean reads were selected from nine RNA-Seq libraries and assembled into 79,729 unigenes. Among these, 33,476 unigenes were assigned to 51 GO subgroups, and 26,117 unigenes were assigned to 20 KEGG secondary metabolic pathways. Next, 2473 differentially expressed genes (DEGs) were divided into three groups, as follows: G-24 h (germinating seeds) vs. D (dormant seeds); G-48 h (germinated seeds) vs. D; and G-48 h vs. G-24 h. From these 2473 DEGs, 8 were selected as candidate dormancy unigenes for the R population if their expression levels continuously decreased during the seed germination progress and their functional annotations were related to plant seed dormancy. One candidate unigene was annotated as CYP707A2; two unigenes were annotated as the transcription factors TGA4 and TGA2; one unigene was annotated as the cystathionine beta-synthase gene; and four unigenes could not be annotated as any gene listed in the six public databases. However, qRT-PCR-validated results showed that, during the germination of R seeds, the expression of the three candidate unigenes first decreased and then increased, indicating that they may have other growth-regulating functions in R populations. In brief, the dormancy function of the eight candidate dormancy unigenes needs to be further studied. [ABSTRACT FROM AUTHOR]

The ancient crop broomcorn millet (Panicum miliaceum L.) is an indispensable orphan crop in semi‐arid regions due to its short life cycle and excellent abiotic stress tolerance. These advantages make it an important alternative crop to increase food security and achieve the goal of zero hunger, particularly in light of the uncertainty of global climate change. However, functional genomic and biotechnological research in broomcorn millet has been hampered due to a lack of genetic tools such as transformation and genome‐editing techniques. Here, we successfully performed genome editing of broomcorn millet. We identified an elite variety, Hongmi, that produces embryogenic callus and has high shoot regeneration ability in in vitro culture. We established an Agrobacterium tumefaciens‐mediated genetic transformation protocol and a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9‐mediated genome‐editing system for Hongmi. Using these techniques, we produced herbicide‐resistant transgenic plants and edited phytoene desaturase (PmPDS), which is involved in chlorophyll biosynthesis. To facilitate the rapid adoption of Hongmi as a model line for broomcorn millet research, we assembled a near‐complete genome sequence of Hongmi and comprehensively annotated its genome. Together, our results open the door to improving broomcorn millet using biotechnology. [ABSTRACT FROM AUTHOR]

Amaranthus hybridus L. is a major weed for summer crops. Although A. hybridus has been a known crop weed in the Republic of South Africa (RSA) for a long time, herbicide resistance has not been a problem. Nevertheless, A. hybridus populations from KwaZulu Natal (KZN) Province have caught the attention of farmers since glyphosate has been progressively becoming less effective in controlling the species. This study aimed to evaluate herbicide resistance in A. hybridus and the underlying mechanisms of resistance. Seeds from 50 glyphosate‐resistant plants were collected from fields at Bergville and Winterton in KZN and compared with a susceptible population from Hendrina (Mpumalanga Province). Glasshouse screening was conducted where glyphosate (Roundup® PowerMax) was applied at 6‐leaf stage, at doses 0, 540, 1080 (recommended dose), 2160 and 4320 g ae ha−1. Surviving plants were sampled for molecular analysis to establish any target site mutations in the EPSPS gene that confer glyphosate resistance. Dose–response assay indicated 100% control in the Hendrina population, variation in the control of the Winterton population and 100% survival in the Bergville population. Molecular analysis indicated a rare triple mutation (TAP‐IVS) in the KZN populations. This kind of mutation endows a high level of glyphosate resistance, which explains why these populations survived even the 4× dose. These findings confirmed the first cases of glyphosate‐resistant A. hybridus and established the mechanism of resistance as target site mutations in the EPSPS gene reported in the RSA. These findings will serve as a base for other herbicide resistance cases and the development of initiatives to control and minimize the spread of this weed in the RSA. [ABSTRACT FROM AUTHOR]

With intensive and extensive using herbicides, the level of weed resistance was increased, new resistance mechanisms are constantly being discovered. Adcances on the mechanisms of target-site resistance (TSR) and non-target-site resistance (NTSR) in recent ten years were summarized in this paper. The progress of TSR mainly included new resistance mutation in herbicide target enzymes of acetolactate synthase, acetyl-CoA carboxylase and 5-enolpyruvylshikimate-3-phosphatesynthase, as well as various resistance mutations occurring in target enzyme and multiple mutated target isozymes that resisting stronger herbicide selection. In addition, the roles of NTSR in glyphosate resistance of cytochrome P450 (CYP81), aldo-keto reductase and ABC transporter protein (EcABCC8) were also described in detail. This paper is beneficial for understanding the molecular mechanisms and evolutionary laws of weed resistance from more profound and comprehensive perspective, and also provides inspriration for scientifically using herbicides and designing new herbicides with new mode of action. [ABSTRACT FROM AUTHOR]

Dry direct-seeding can get rid of the constraints of high-water demand, and is the simplest and most laborsaving mode in rice (Oryza sativa L.) cultivation. However, weeds are more prone to occur in dry direct-seeding rice fields, coupled with increased herbicide resistance, leading to confusion among growers regarding herbicide selection. In this study, our investigation results revealed total grass quantity reached 458.82 plants m-2. Two round of field experiments were conducted to determine suitable post-emergence herbicides for dry directseeding indica rice. The results showed that among the herbicides safe to indica rice, the efficacy of the combination of pyraquinate (a new 4-hydroxyphenylpyruvate dioxygenase inhibitor, 150.0 g ai ha-1) + florpyrauxifen-benzyl (13.5 g ai ha-1) on Leptochloa chinensis (L.) Nees, Eclipta prostrata (L.) L., Cyperus iria L., Fimbristylis miliacea auct., and total grasses were 89.1%, 97.8%, 97.2%, 90.1%, and 92.8%, respectively; the efficacy of metamifop (120.0 g ai ha-1) + florpyrauxifen-benzyl (18.0 g ai ha-1) and 22.0% cyhalofop-butyl + pyrazosulfuron-ethyl + bispyribac-sodium OD (148.5 g ai ha-1) on main weeds also exceeds 85.0%, except for cyhalofop-butyl-resistant L. chinensis. The combination of metamifop + florpyrauxifen-benzyl and 22.0% cyhalofop-butyl + pyrazosulfuron-ethyl + bispyribac-sodium OD can be selected for fields where L. chinensis is not resistant to acetyl-CoA carboxylase (ACCase) inhibitors. The combination of pyraquinate + florpyrauxifenbenzyl is the most promising combination to control multiple weeds, even ACCase inhibitors-resistant weeds. This study could also provide references for herbicides selection and management of ACCase inhibitors-resistant L. chinensis in dry direct-seeding indica rice field worldwide. [ABSTRACT FROM AUTHOR]

Multiple herbicide-resistant kochia (Bassia scoparia (L.) A.J. Scott) has grown in prevalence in the canola (Brassica napus L.) production region of North America. Glufosinate-resistant canola facilitates kochia management since glufosinate-resistant kochia is not known to occur. Field experiments were conducted from 2013 to 2015 in five environments near Lethbridge and Coalhurst, Alberta, to identify herbicide strategies targeting acetolactate synthase inhibitor-resistant kochia with and without glyphosate resistance in glufosinate-resistant canola. Sequential glufosinate treatments (500 g ai ha−1) postemergence (POST) caused excellent (≥90%) kochia control and biomass reduction across environments. Preplant (PP) carfentrazone + sulfentrazone (9 + 105 g ai ha−1) alone or followed by (fb) POST glufosinate (9 + 27 fb 500 or 9 + 105 fb 500 g ai ha−1) resulted in excellent kochia control in all environments tested. PP carfentrazone + sulfentrazone (9 + 53 g ai ha−1) alone, and a single POST treatment with glufosinate (500 or 590 g ai ha−1) alone or preceded by fall-applied ethalfluralin (1100 fb 500 g ai ha−1) with or without PP carfentrazone (1100 fb 9 fb 500 g ai ha−1) caused ≥80% kochia control and biomass reduction in all environments tested. However, treatments containing PP carfentrazone + sulfentrazone caused unacceptable canola injury or yield loss in at least one environment. In conclusion, single or sequential treatments of glufosinate POST managed multiple herbicide-resistant kochia effectively in canola. Layering fall-applied/PP ethalfluralin and/or PP carfentrazone with glufosinate POST may help alleviate resistance selection pressure placed on glufosinate in canola. [ABSTRACT FROM AUTHOR]

The evolution and spread of herbicide-resistant weeds threatens long-term sustainability of Canadian agro-ecosystems. Herbicide-resistant weeds increase management inputs and costs, increase off-target and environmental exposure to pesticides, reduce yield quality and quantity, and impede harvest efficiency. Amaranthus species including Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp (Amaranthus tuberculatus (Moq.) J.D. Sauer) are particularly concerning due to both their propensity towards herbicide resistance evolution, their history of invasion, and their spread in agro-ecosystems. A biovigilance approach is taken to build awareness of these pigweeds' initial invasion and spread in the USA. Characteristics of their identification, potential hybridization, and known herbicide resistance evolution are reviewed. Fourteen species of Amaranthus are found in Canada, nine of which (including waterhemp) possess herbicide-resistant biotypes. A total of 45 hybrids between various Canadian Amaranthus species with each other or Palmer amaranth have been noted. Hybrids have been experimentally produced or observed from herbarium specimens, with three cases of herbicide resistance transfer notably with Palmer amaranth or waterhemp. Mitigation strategies will depend on successful species identification and herbicide resistance status determination. Common pathways for Palmer amaranth introductions in the northern USA include both animal feed systems with grain screenings and crop production systems including seed and equipment contamination. Regional awareness campaigns will be critical to support Canadian farmers in identifying and quickly mitigating invasions of Palmer amaranth and waterhemp to prevent establishment and spread of infestations into new areas. [ABSTRACT FROM AUTHOR]