Search Results (35)

Goosegrass (Eleusine indica) is a major weed in Brazilian soybean, corn, and cotton systems, infesting over 60% of grain-producing areas and potentially reducing yields by more than 50%. Its competitiveness is due to its rapid emergence, fast tillering, C4 metabolism, and adaptability to various environmental conditions. A critical challenge relates to its widespread resistance to multiple herbicide modes of action, notably glyphosate and acetyl-CoA carboxylate (ACCase) inhibitors. Resistance mechanisms include 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) target-site mutations, gene amplification, reduced translocation, glyphosate detoxification, and mainly ACCase target-site mutations. This literature review summarizes the current knowledge on herbicide resistance in goosegrass and its management in Brazil, with an emphasis on integrating chemical and non-chemical strategies. Mechanical and physical controls are effective in early or local infestations but must be combined with chemical methods for lasting control. Herbicides applied post-emergence of weeds, especially systemic ACCase inhibitors and glyphosate, remain important tools, although widespread resistance limits their effectiveness. Sequential applications and mixtures with contact herbicides such as glufosinate and protoporphyrinogen oxidase (PPO) inhibitors can improve control. Pre-emergence herbicides are effective when used before or immediately after planting, with adequate soil moisture being essential for their activation and effectiveness. Given the complexity of resistance mechanisms, chemical control alone is not enough. Integrated weed management programs, combining diverse herbicides, sequential treatments, and local resistance monitoring, are essential for sustainable goosegrass management. Full article

Based on the complaints of malt barley growers about the insufficient control of rigid ryegrass (Lolium rigidum Gaudin) after applying the ACCase inhibitor pinoxaden, a survey was conducted during the early spring growing season of 2019/20; 20 barley fields located in Thessaloniki and 20 fields in Serres were marked with poor weed control levels. Before the barley harvest, representative weed seeds were collected from all 40 fields. After performing seed germination tests, fourteen populations (six from Thessaloniki and eight from Serres) with the highest seed germination ability were selected for further study. The whole-plant dose–response assays conducted in 2019–2020 indicated that most of the populations were multi-resistant to ACCase and ALS inhibitors. The estimated GR₅₀ values (the herbicide dose required to reduce the fresh weight of treated plants by 50%) for pinoxaden and mesosulfuron-methyl + iodosulfuron-methyl-sodium ranged from 1.15 to 52.41 g ai ha⁻¹ and 4.75 to 31.25 g ai ha⁻¹, respectively. Furthermore, the sequencing of acccase gene fragments from plants that survived pinoxaden application revealed that 11 out of 14 plant populations had a double accase point mutation at Ile1781 and Ile2041 codons. In addition, the sequencing of als gene fragments from the plants that survived mesosulfuron-methyl + iodosulfuron-methyl-sodium application revealed that 11 out of 14 plant populations had a point mutation at the Pro197 codon and 2 of them had a second als mutation at the Trp574 codon. These findings indicate that L. rigidum populations are multi-resistant to ACCase and ALS inhibitors, with individuals exhibiting either double accase or double als mutations. Full article

Flusulfinam is a 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide applied post-emergence (POST) to control Echinochloa crus-galli (L.) P.Beauv., Leptochloa chinensis (L.) Nees, Digitaria sanguinalis (Linn.) Scop. and other annual weeds in directly seeded and transplanted paddy fields in China, registered in September 2024. Notably, compared with other HPPD inhibitors in rice, flusulfinam exhibits consistently high safety in both japonica and indica rice varieties. Meanwhile, flusulfinam has no target-site cross-resistance with traditional acetolactate synthase (ALS)-inhibiting, acetyl-CoA carboxylase (ACCase)-inhibiting, and auxin herbicides. Moreover, as the only heterocyclic-amide-structured herbicide in the HPPD inhibitors, it poses a low risk of metabolic cross-resistance with the other HPPD inhibitors, making it a promising candidate for managing herbicide-resistant weeds in rice fields. In this study, the baseline sensitivity to flusulfinam of E. crus-galli and L. chinensis in paddy fields in China was established using dose–response assays between June and October 2023. Thirty-nine populations of E. crus-galli and forty-three populations of L. chinensis, collected from rice fields across various major rice-producing regions in China, exhibited susceptibility to flusulfinam. The GR₅₀ values ranged from 0.15 to 19.39 g active ingredient (a.i.) ha⁻¹ for E. crus-galli and from 7.82 to 49.92 g a.i. ha⁻¹ for L. chinensis, respectively, far below the field recommended rate of flusulfinam. Meanwhile, the GR₅₀ values of E. crus-galli and L. chinensis to flusulfinam were both distributed as a unimodal curve, with baseline sensitivity (GR₅₀b) of 6.48 g a.i. ha⁻¹ and 22.38 g a.i. ha⁻¹, respectively. The SI₅₀ value showed 129.27-fold and 6.38-fold variability in flusulfinam sensitivity among the 39 E. crus-galli field populations and 43 L. chinensis filed populations, while the variability declined to 2.99-fold and 2.23-fold when the SI₅₀b value was used. This study substantiated the efficacy of flusulfinam against E. crus-galli and L. chinensis in Chinese paddy fields and furnished a benchmark for monitoring temporal variations in the susceptibility of field populations of E. crus-galli and L. chinensis to flusulfinam. Full article

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. Full article

To develop aryloxyphenoxypropionate herbicides with novel structure and improved activity, a total of twenty-eight novel quinazolinone–phenoxypropionate derivatives containing a diester moiety were designed and synthesized. The herbicidal bioassay results in the greenhouse showed that QPEP-I-4 exhibited excellent herbicidal activity against E. crusgalli, D. sanguinalis, S. alterniflora, E. indica, and P. alopecuroides with inhibition rates >80% at a dosage of 150 g ha⁻¹ and displayed higher crop safety to G. hirsutum, G. max, and A. hypogaea than the commercial herbicide quizalofop-p-ethyl. Studying the herbicidal mechanism by phenotypic observation, membrane permeability evaluation, and transcriptomic analysis revealed that a growth inhibition of plants by QPPE-I-4 was the result from damage of the plants’ biomembrane. The evaluation of ACCase activity in vivo indicated that QPPE-I-4 could inhibit ACCase and may be a new type of ACCase inhibitor. The present work indicated that QPPE-I-4 could represent a lead compound for further developing novel AOPP herbicides. Full article

Large crabgrass (Digitaria sanguinalis (L.) Scop.) is one of the major malignant grass weeds in Chinese maize (Zea mays L.) fields, and it has recently developed resistance to the acetolactate synthase (ALS)-inhibiting herbicide nicosulfuron. This study focused on a suspected nicosulfuron-resistant (R) population (LJ-01) of D. sanguinalis, collected from Lujiang County in Anhui Province, China, to explore the resistance level and potential resistance mechanism. Whole-plant dose–response testing confirmed that the LJ-01 population evolved a high level of resistance to nicosulfuron (11.5-fold) compared to the susceptible (S) population, DY-02. The ALS gene sequencing and relative expression assay of the R plants indicated that target gene mutation and overexpression were not responsible for the resistance phenotype. However, pretreatment with malathion, a known cytochrome P450 monooxygenase (P450) inhibitor, alleviated the resistance of the R population to nicosulfuron by approximately 36%. High-performance liquid chromatography (HPLC) analysis revealed that the R plants metabolized nicosulfuron faster than the S plants. Moreover, cross-resistance testing suggested that the R population exhibited low levels of resistance to thifensulfuron-methyl and pyrazosulfuron-ethyl, but it remained susceptible to rimsulfuron. Multiple resistance patterns showed that the R population evolved low resistance to the photosystem inhibitors bromoxynil octanoate and atrazine and sensitivity to the acetyl-CoA carboxylase (ACCase) inhibitor cyhalofop-butyl and the 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors tembotrione, mesotrione, and topramezone. This study reports, for the first time, the simultaneous resistance to ALS and different photosystem inhibitors in D. sanguinalis. The nicosulfuron resistance observed in the R population could primarily be attributed to an enhanced metabolism involving P450 enzymes. Full article

Three perennial ryegrass (Lolium perenne) populations (R1, R2, and R3) with suspected resistance (R) to acetolactate synthase (ALS) or acetyl-CoA carboxylase (ACCase) herbicides were collected from wheat (Triticum aestivum) fields in northwestern Greece to study the underlying mechanisms of resistance and their impact on growth rate and competitive ability against wheat. Preemergence and postemergence plant dose–response assays showed that the R1 population was cross-resistant to the ALS inhibitors chlorsulfuron, mesosulfuron + iodosulfuron, and pyroxsulam, but susceptible (S) to imazamox. However, all populations were susceptible to the ACCase inhibitors clodinafop-propargyl, clethodim, diclofop-methyl, and pinoxaden. The analysis of the ALS gene sequence revealed a substitution of Pro197 by His or Leu in the ALS enzyme in L. perenne, which is reported for the first time in this weed and indicates a potential mechanism of target site-mediated resistance. The R1 population grown in the absence or presence of wheat competition displayed similar aboveground biomass and tiller number trends, and therefore similar estimated growth rates. In addition, the aboveground biomass of wheat was similarly reduced by both the R1 and S populations, supporting the evidence of their similar competitive ability against wheat. In general, these findings indicate that there is no clear evidence for the fitness advantage of R1 over the S population. Full article

Resistance of blackgrass (Alopecurus myosuroides Huds.) and silky bentgrass (Apera spica-venti (L.) P. Beauv.) to ACCase inhibitors is a serious issue in winter cereals throughout Europe, especially as hormesis induced by herbicides has been observed in some populations. According to the literature, growth-stimulating herbicide rates are on the rise. The aim of this study was to assess the responses of A. myosuroides and A. spica-venti, which are potentially resistant to ACCase inhibitors, to fenoxaprop-P-ethyl and pinoxaden applied at rates up to 8 times greater than their registered rates. The reaction of A. myosuroides to fenoxaprop-P-ethyl and pinoxaden resulted in an increase in biomass gain in six and four populations, respectively. In one population of A. myosuroides, this increase was statistically significant (46.4% and 55.3%). All three potentially resistant A. spica-venti populations tested were at least partially stimulated by fenoxaprop-P-ethyl, while pinoxaden only stimulated the APSII population (significant increase of 43.8%). Predictions of the possible impact of herbicides on the reproductive potential of the tested populations allow genotypes to be identified whose reproduction may be stimulated by the herbicides. The results of this study indicate that the tested populations can induce mechanisms that reduce the negative impact of the applied herbicides, with some populations demonstrating the effect of stimulating the accumulation of biomass in the treated plants. Full article

Italian ryegrass (Lolium multiflorum L.), a cross-pollinated grass, is gradually becoming a predominant weed in wheat fields in China and is evolving resistance to many groups of herbicides. The aim of this study is to determine the resistance levels of a single L. multiflorum population from a wheat field in Henan Province China, to three modes of action (MoAs) of herbicides and to further characterize the potential resistance mechanisms. This L. multiflorum population evolved multiple herbicide resistances to pyroxsulam [acetolactate synthase (ALS)], pinoxaden [acetyl-CoA carboxylase (ACCase)] and isoproturon [photosystem II (PSII)]. Target-site resistance (TSR) mutations (Pro-197-Gln, Pro-197-Thr, and Trp-574-Leu) and non-target-site resistance (NTSR) mediated by cytochrome P450 monooxygenase (CYP450) genes were associated with pyroxsulam resistance. Pinoxaden resistance was conferred by two TSR mutations, which referred to a rare Ile-2041-Val mutation and a common Ile-1781-Leu mutation but with two different nucleotide substitutions (CTA/TTA). CYP450- and glutathione-S-transferase (GST)-mediated resistances were the main resistance mechanisms for this multiple herbicide-resistant (MHR) population to the PSII inhibitor isoproturon. This is the first case of a single L. multiflorum population evolving multiple resistance to three herbicide MoAs (ALS, ACCase and PSII) in China. Diverse resistance mechanisms including TSR and NTSR mean L. multiflorum exhibits a high degree of resistance plasticity. Full article

Chloris virgata is one of the most problematic summer grass species in southeastern Australia. A total of 40 populations of C. virgata were evaluated in the spring–summer season of 2021–2022 in an open environment at the Gatton Farms of the University of Queensland, Queensland, Australia, for their response to two acetyl-coenzyme-A carboxylase (ACCase) inhibitors (clethodim and haloxyfop), a 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) inhibitor (glyphosate), and an acetolactate synthase (ALS) inhibitor (imazapic). In the first experiment, all populations were screened at the field rate of each herbicide, and the second experiment evaluated the response of seven populations of C. virgata to different rates of glyphosate and imazapic. There were three replications of each treatment and both experiments were repeated over time. None of the populations survived the field rate of clethodim and haloxyfop, possibly suggesting a low exposure of the populations to these herbicides. Individuals in about 90% of populations survived (1% to 100% of individuals surviving) the field rates of glyphosate and individuals in all populations survived (1% to 100%) the imazapic field rate. The dose-response study revealed up to 14- and 5-fold glyphosate resistance in C. virgata populations based on survival and biomass values, respectively, compared to the most susceptible population. Imazapic resistance was up to 2.3- and 16-fold greater than the most susceptible population in terms of survival and biomass values, respectively. The increased cases of glyphosate- and imazapic-resistant C. virgata warrant a nationwide survey and diversified management strategies. Full article

Asia minor bluegrass (Polypogon fugax) is a common and problematic weed throughout China. P. fugax that is often controlled by acetyl-CoA carboxylase (ACCase) inhibitors in canola fields. Herein, we confirmed a P. fugax population (R) showing resistance to all ACCase inhibitors tested with resistance indexes ranging from 5.4–18.4. We further investigated the resistance mechanisms of this R population. Molecular analyses revealed that an amino acid mutation (Asp-2078-Gly) was present in the R population by comparing ACCase gene sequences of the sensitive population (S). In addition, differences in susceptibility between the R and S population were unlikely to be related to herbicide metabolism. Furthermore, a new derived cleaved amplified polymorphic sequence (dCAPS) method was developed for detecting the Asp-2078-Gly mutation in P. fugax efficiently. We found that 93.75% of plants in the R population carried the Asp-2078-Gly mutation, and all the herbicide-resistant phenotype of this R population is inseparable from this mutation. This is the first report of cross resistance to ACCase inhibitors conferred by the Asp-2078-Gly target-site mutation in P. fugax. The research suggested the urgent need to improve the diversity of weed management practices to prevent the widespread evolution of herbicide resistance in P. fugax in China. Full article

Chinese sprangletop (Leptochloa chinensis (L.) Nees) is recognized as the most disturbing weed in rice fields in Africa, Australia, and Asia due to causing a significant reduction in yields. The habit of most lowland rice farmers in Indonesia is using high doses of herbicides more than once without any rotation, leading to increased weed resistance potential. Therefore, this study aimed to confirm the resistance level of L. chinensis to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides using the whole-plant pot test method. We identified other herbicides that can control the resistant biotype and performed DNA sequencing on a sample to determine mutations present in the biotype′s ACCase gene through polymerase chain reaction. The herbicide dose–response experiment showed that the L. chinensis from Bantimurung Subdistrict, Maros Regency, South Sulawesi, exhibited resistance to ACCase inhibitors (metamifop and cyhalofop-butyl), which is the first case of resistance to ACCase herbicides reported in Indonesia. An acetolactate synthase inhibitor (bispyribac-sodium) and a 1-deoxy-d-xylulose-5-phosphate synthase (DOXP) inhibitor (clomazone) were effective at controlling the resistant biotypes of L. chinensis, so could considered for use in rotation or as an ingredient in mixed herbicides. Single-nucleotide substitution of guanine for thiamine at position 6081 (TGG; susceptible, TGT; Maros) that causes a Trp₂₀₂₇Cys mutation in the target gene contributes to the resistance of the Maros biotype to ACCase inhibitors. Full article

Glyamifop (R&D code: FG001), (R)-(2-(4-(6-chlorobenzoxazol-2-oxy) phenoxy) propionyl) glycine ethyl ester is a newly developed aryloxyphenoxypropionate (HRAC Group 1) herbicide for weed control in paddy fields. This work determined the effect of Glyamifop on weeds and its safety for rice in the glasshouse. Glyamifop controlled the common gramineous weeds in paddy fields at 100 g a.i. ha⁻¹: the fresh weight inhibition rates of Echinochloa crus-galli, Leptochloa chinensis, Setaria viridis, Eragrostis japonica, Digitaria sanguinalis and Panicum bisulcatum were all above 90%. It has almost no inhibitory effect on broad-leaved and cyperaceae weeds, such as Eclipta prostrata and Cyperus iria. Glyamifop inhibited cyhalofop-butyl-resistant L. chinensis, penoxsulam-resistant E. crus-galli and quinclorac-resistant E. crusgalli var. zelayensis by 100%, 99.98% and 96.37%, respectively, at 100 g a.i. ha⁻¹, based on the fresh weight. The selectivity index of Glyamifop foliage treatment in the rice varieties japonica ‘Huaidao 5’, indica ‘Xiangliangyou 900’ and glutinous ‘Zhennuo 29’ was 5.93, 6.81 and 4.91, respectively; therefore, Glyamifop is safe for the 3 different rice varieties. Fresh weight rice inhibition rates were 7.18%, 2.99% and 7.93% at the 2.5-, 3.5- and 5.5-leaf stage, respectively, and the selectivity index was 5.18, 6.04 and 7.93, respectively, indicating that Glyamifop was safe for rice at these leaf stages. L. chinensis ACCase activity decreased with increasing Glyamifop concentration, and the inhibitory effect was similar to that of cyhalofop acid; this confirmed that Glyamifop is an ACCase inhibitor. In conclusion, Glyamifop has potential for the management of gramineous weeds as it has good activity against weeds that are resistant to common herbicides in paddy fields. Full article

Roegneria kamoji Ohwi (Poaceae), a wild relative plant of wheat which is widely distributed across China, has become a dominant and problematic weed in wheat fields in some regions. We have previously confirmed that R. kamoji is highly tolerant to foliar-applied acetyl-CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors in wheat (Triticum aestivum L.). The sensitivity of R. kamoji to pre-emergence (PRE) herbicides and the basis of fenclorim increase selectivity to butachlor between wheat and R. kamoji were evaluated in this study. Screenhouse bioassay showed that R. kamoji exhibited similar sensitivity to wheat to PRE herbicides at their recommended field doses (RFD); it also showed that buatchlor provides the highest relative control for R. kamoji (53.4% emergence and 81.5% fresh weight reduction, respectively), while it had no impact on seedling emergence of wheat among the six PRE herbicides. When butachlor was applied at four-fold RFD, no R. kamoji seedlings emerged; however, it significantly reduced the above-ground biomass of wheat compared with the non-treated control. Pre-treatment with herbicide safener fenclorim by seed soaking increased the ED₁₀ value of butachlor to wheat from 221.8 to 1600.1 g a.i. ha⁻¹, thus increasing the selectivity index from 9.6 to 68.9 between wheat and R. kamoji. The activities of α-amylase activity and protein content during germination, and glutathione-S-transferase (GST) and β-ketoacyl-CoA synthase (KCS) in the seedlings, could be induced by butachlor in both wheat seeds with or without fenclorim pre-soaking. These results suggested that butachlor provides the highest control for R. kamoji and did not affect germination and emergence in wheat. The basis of fenclorim-increased selectivity to butachlor was associated with the induced GST and KCS-mediated enhanced herbicide metabolism in wheat. Full article

A population of Echinochloa crus-galli (L.) P. Beauv obtained from direct-seeding rice fields in Jiangxi Province, China, exhibited high resistance levels (13.5-fold) to the acetyl-CoA carboxylase (ACCase)-inhibiting herbicide cyhalofop-butyl. Compared with the susceptible (S) population, this resistant (R) population evolved a cross-resistance to aryloxyphenoxypropionates (APPs) herbicides metamifop (2.9-fold) and fenoxapro-p-ethyl (4.1-fold), cyclohexanediones (CHDs) herbicide clethodim (4.7-fold), phenyl pyrazoline (DEN) herbicide pinoxaden (6.4-fold), and evolved multiple-resistance to acetolactate synthase (ALS)-inhibiting herbicide penoxsulam (3.6-fold), and auxin mimic herbicides quinclorac (>34.7-fold) and florpyrauxifen-benzyl (2.4-fold). ACCase gene sequencing did not reveal the existence of any known mutation point conferring with herbicide resistance. In addition, three metabolic inhibitors—one glutathione—S-transferase (GST) inhibitor (NBD-Cl), and two cytochrome P450 inhibitors (malathion and PBO)—did not reverse the cyhalofop-butyl resistance. Furthermore, enhanced metabolic rates of more than 60% 24 h after treatment with the active compound cyhalofop acid was observed in R plants compared to S plants. Hence, enhanced metabolism activity endows a non-target-site resistance to cyhalofop-butyl in the R population of E. crus-galli. Future research will be required to determine what metabolizing enzyme genes are responsible for cyhalofop-butyl resistance in E. crus-galli. Full article