Resistance to protoporphyrinogen oxidase (PPO) inhibitors in Palmer amaranth is a major concern, given the high selection pressure and increasing number of populations with reduced sensitivity to PPO herbicides in the US. We evaluated the effect of five soil-applied herbicides on Palmer amaranth (Amaranthus palmeri S. Wats.) populations collected in 2014 and 2015 in Arkansas, USA. Soil-applied saflufenacil, sulfentrazone, and flumioxazin reduced the seedling emergence 91–100%; however, fomesafen and oxyfluorfen showed reduced (63–90%) efficacy on some populations. Target-site mutation (TSM) is the major mechanism of resistance to PPO herbicides; therefore, six populations showing resistance to soil-applied fomesafen were selected for molecular investigations. A total of 81 survivors were genotyped for all known resistance-conferring mutations. A total of 64% and 36% survivors had single and double TSMs, respectively, with 69% of plants carrying TSM in both alleles of PPO2. Three survivors from two populations showed an additional copy of PPO2, whereas all other survivors had one copy. Expression analysis showed 3- to 6-fold upregulation of PPO2 in all plants from resistant populations tested. Transgenic overexpression of WT-ApPPO2 and dG210-Apppo2 in A. thaliana confirmed the reduced sensitivity to soil-applied fomesafen compared to the wild type. Collectively, PPO inhibitors applied pre-emergence are still effective in controlling populations resistant to foliar-applied PPO herbicides. Mechanically, elevated expression of resistant PPO2, alongside functional TSM, contribute to reduced sensitivity to soil-applied fomesafen. 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

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

Asia Minor bluegrass (Polypogon fugax Nees ex Steud.) is a problematic grass weed of winter crops in China, where some populations have become resistant to herbicides. Previously, we identified a P. fugax population QS exhibiting target-site-based resistance (TSR) and non-target-site-based resistance (NTSR) to clodinafop-propargyl. This study aims to understand the metabolic resistance to clodinafop-propargyl between susceptible (XC) and resistant (QS) populations of P. fugax in the seedling and tillering stage, separately. Several differentially expressed candidate genes in the seedling and tillering stages were identified by RNA-Seq, including three P450 family genes, one glutathione S-transferase (GST) gene, and two ATP-binding cassette transporters. Additionally, we discovered a GST gene that was significantly differentially expressed in the resistant population during the seedling stage, as well as three peroxidase genes that were presumed to be related to NTSR metabolism. Three other peroxidase genes and one esterase were presumed to be related to NTSR metabolism during the tillering stage of the resistant population. Overexpression of the three randomly selected candidate genes can enhance herbicide-resistance in Arabidopsis transgenic plants. This study provided a novel insight into herbicide metabolism regulation genes during the different growth stages of resistant P. fugax population. Full article

Dicamba plus glyphosate (DpG) tank mixture has been widely adopted for broad-spectrum weed control. However, recent studies indicated antagonistic interactions between these herbicides. Furthermore, little is known about the effect of non-ammonium sulfate water conditioner (non-AMS WC) adjuvant on the activity of DpG tank mixture. Thus, the present study was elaborated to evaluate (1) the interaction of DpG tank mixtures combinations on barnyardgrass, and glyphosate-susceptible (GS) and -resistant (GR) horseweed control, and (2) the effect of non-ammonium sulfate water conditioner (non-AMS WC) on the interaction of those two herbicides on the aforementioned weed species. Greenhouse experiments were conducted in 2020 at the Pesticide Application Laboratory in North Platte, NE. Herbicide treatments were arranged in a two-level factorial design of six dicamba rates by six glyphosate rates for Study 1, and in a three-level factorial design of two adjuvant treatments (presence or not of non-AMS WC) by four dicamba rates by four glyphosate rates for Study 2. Both trials were conducted as randomized complete block designs with four replications and two runs. Antagonistic interactions were observed throughout DpG treatments in GS and GR horseweed. For instance, dicamba (560 g ae ha⁻¹) and glyphosate (1260 g ae ha⁻¹) resulted in 72% of GR horseweed biomass reduction, compared to 81% of estimated biomass reduction. For barnyardgrass, antagonistic interactions were only observed within the reduced glyphosate rates. The addition of non-AMS WC had no effect on DpG antagonism. However, it improved the barnyardgrass control by glyphosate. Full article

Bispyribac-sodium (BS) is an herbicide often used to control weeds in rice fields. Hydrogen-rich water (HRW) has recently been recommended for alleviating adverse effects, but whether and how HRW alleviates the injury to rice from exposure to BS is still largely unknown. In this study, a greenhouse hydroponic experiment showed that BS alone could substantially inhibit the plant height and fresh weight of both indica and japonica rice seedlings. For indica rice, its pretreatment with HRW at 75% saturation could markedly alleviate the impact on its size but not so with either 50% or 100% HRW. For japonica rice, all the concentrations of HRW used in this study (50%, 75%, and 100% HRW) were capable of reversing the plant size reductions. Further results revealed that the HRW supplement could increase the activity of antioxidative enzymes, including that of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), which assist in the effective removal of ROS (reactive oxygen species). Subsequent results demonstrated a weaker inhibition of the acetolactate synthase (ALS) enzyme within five days by BS in rice seedlings pretreated with HRW than those receiving the BS treatment alone, and that the HRW pretreatment can hasten the rate at which BS is degraded in rice. Taken together, these findings strongly suggest that pretreatment with HRW may offer a promising and effective strategy to improve the ability of rice to tolerate BS. Full article

The Dongting and Poyang Lakes are the important rice growing areas, and the Bohai Rim and Loess Plateau are the main producing areas of apples in China, where glyphosate has been used continuously to control weeds including Eleusine. indica for many years. In this study, the resistance levels and target-site based resistance (TSR) mechanisms to glyphosate in E. indica populations, which were collected from above areas were investigated. A total of 35 out of 50 (70%) E. indica populations have evolved resistance to glyphosate with resistance index (RI) of 2.01~10.43. The glyphosate-resistant (GR) E. indica accumulated less shikimic acid than glyphosate-susceptible (GS) populations, when treated by 1.0 mg/L, 10 mg/L or 100 mg/L glyphosate. There was no mutation at Thr102 and Pro106 in 5-enolpyruvate shikimate-3-phosphate synthase (EPSPS), which endowed glyphosate resistance in E. indica and other weed species. A Pro-381-Leu was found in EPSPS in GR populations. In contrast, the expression level of EPSPS gene was highly correlated with glyphosate resistance in E. indica with a determination coefficient of 0.88. These indicate that the glyphosate resistance in aforementioned E. indica populations was mainly caused by the overexpression of EPSPS, not by amino acid mutation in EPSPS. 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

Tribenuron-methyl-resistant (TmR) cleavers (Galium aparine L.) have been reported around the major winter wheat farming region in China. From 2017 to 2020, cleavers seeds were collected from wheat production fields across Jiangsu Province to evaluate the frequency and distribution of tribenuron-methyl-, bensulfuron-methyl- and halosulfuron-methyl-resistant cleavers, and to assess the frequency of multiple resistance. Here we report resistance frequency as percent resistance within a population, and resistance distribution as the percentage and locations of populations classified as resistant to a discriminating herbicide dose. From 2017 to 2020, cleavers populations were screened with tribenuron-methyl, bensulfuron-methyl and halosulfuron-methyl. The percentages of tribenuron-methyl-resistant cleavers populations from 2017 to 2020 were 53.33%, 51.52%, 52.38% and 47.17%, respectively; and the percentages of cleavers populations with low tribenuron-methyl resistance were 23.33%, 26.67%, 30.00% and 36.67%, respectively. The percentages of bensulfuron-methyl-resistant cleavers populations from 2017 to 2020 were 36.67%, 39.39%, 35.71% and 33.96%, respectively; and the percentages of cleavers populations had low tribenuron-methyl resistance were 30.00%, 40.00%, 53.33% and 23.33%, respectively. The percentages of halosulfuron-methyl-resistant cleavers populations from 2017 to 2020 were 26.67%, 27.27%, 50.00% and 41.51%, respectively; and the percentages of cleavers population with low tribenuron-methyl resistance were 50.00%, 53.33%, 33.33% and 40.00%, respectively. Finally, 26.67%, 22.22%, 19.05% and 20.75% of cleavers populations had resistance to 2-methyl-4-chlorophenoxyacetic acid sodium (MCPA-Na) from 2017 to 2020, respectively; however, all populations were sensitive to fluroxypyr and carfentrazone-ethyl. This confirmation of multiple resistance in cleavers populations emphasizes the importance of diversity in herbicide sites of action as critical to extending the usefulness of remaining effective herbicides such as MCPA-Na, fluroxypyr and carfentrazone-ethyl for the management of this weed. Full article

Barnyardgrass (a monocotyledon) and yerbadetajo (a dicotyledon) are the most troublesome weeds in rice fields in China. The synthetic auxin herbicide florpyrauxifen-benzyl can effectively control both weeds. The objective of this research was to clarify modes of action of florpyrauxifen-benzyl in barnyardgrass and yerbadetajo. Our results showed that yerbadetajo was more sensitive to florpyrauxifen-benzyl than barnyardgrass: the 50% growth rate inhibition in barnyardgrass and yerbadetajo was 4.14 and 0.38 g a.i. ha⁻¹, respectively. Florpyrauxifen-benzyl induced the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and abscisic acid (ABA) in yerbadetajo within 24 h, while in barnyardgrass, the highest production occurred at 12 h and decreased at 24 h. ACC and ABA levels in yerbadetajo at 24 h of treatment were significantly higher than those in barnyardgrass at any time. There were less differentially expressed genes related to ethylene and ABA synthesis in barnyardgrass than in yerbadetajo. There were five genes induced to increase by florpyrauxifen-benzyl in barnyardgrass and eleven genes in yerbadetajo. More ACC oxidase genes (ACO) were induced in barnyardgrass and more ACC synthesis genes (ACS) in yerbadetajo, especially three ACS3 (>30 fold). We speculated that differences in gene expression caused differences in ethylene and ABA production, leading to differences in phytotoxicity. Full article

Italian ryegrass (Lolium multiflorum Lam.) was introduced into China as a kind of turfgrass and has invaded wheat fields of the Huang-Huai-Hai Plain, causing great losses to grain yield. The acetyl–CoA carboxylase (ACCase) inhibitor clodinafop-propargyl and the acetolactate synthase (ALS) inhibitor mesosulfuron-methyl are highly efficient herbicides that have been widely used for control of this species, which has also resulted in its resistance evolution. However, the resistance status of L. multiflorum in the Huang-Huai-Hai Plain of China remains unclear, which hinders the integrated management of this weed in winter wheat production systems. In the current study, a total of 37 L. multiflorum populations were collected from the wheat fields across the region, and their susceptibility to clodinafop-propargyl and mesosulfuron-methyl was assessed. Of these, 13 populations were resistant or evolving resistance to clodinafop-propargyl (R?, RR, and RRR) with resistance index (RI) ranging from 2.62 to 830.05, and 8 populations were resistant or evolving resistance to mesosulfuron-methyl (R? and RR) with RI ranging from 3.89 to 16.68. Seven populations showed multiple-resistance to both clodinafop-propargyl and mesosulfuron-methyl. Three ACCase (I1781L, I2041N, and D2078G) and four ALS (P197T, P197S, P197A, and W574L) resistance mutations were identified in the herbicide-resistant populations, and I1781L and P197T were predominant ACCase and ALS mutations, respectively. Real-time quantitative PCR assays showed that compared with the susceptible population, the ACCase expression was slightly upregulated in some of the clodinafop-propargyl-resistant populations (AH-01 and AH-05) following clodinafop-propargyl treatment, while the ALS expression in the mesosulfuron-methyl-resistant populations showed no significant change following mesosulfuron-methyl treatment. Whole-plant dose-response testing showed that the AH-01 population carrying an ACCase gene I2041N mutation exhibited cross-resistance to all the ACCase inhibitors tested and multiple-resistance to the ALS inhibitor bispyribac-sodium, the AH-05 population carrying an ACCase gene I1781L mutation and an ALS gene P197T mutation showed cross-resistance to all the ACCase and ALS inhibitors tested, and the HN-07 population carrying an ACCase gene D2078G mutation showed cross-resistance to all the ACCase inhibitors tested and multiple-resistance to some ALS inhibitors. All the resistant populations remained susceptible to the 5-enolpyruvylshikimate-3-phosphate inhibitor glyphosate and the photosystem II inhibitor isoproturon. This study has clarified the distributions of clodinafop-propargyl- and/or mesosulfuron-methyl-resistant L. multiflorum in the Huang-Huai-Hai Plain of China, and target gene mutation was one of the most common mechanisms responsible for the resistance. Full article

Black-grass (Alopecurus myosuroides Huds.) is a common weed in Chinese wheat fields, and has become troublesome due to its evolution of herbicide resistance. One black-grass population (HN-14) collected from a wheat field where herbicides were applied was suspected to be resistant (R) to mesosulfuron-methyl. This study aims to establish a cross-resistance pattern and explore potential resistance mechanisms. The results of a whole-plant dose response assay showed that the resistant (R) population had a high of resistance to mesosulfuron-methyl (33-fold); meanwhile, no synergism of P450s activity inhibitor malathion was observed. The sequencing results revealed that ALS resistance mutation Trp-574-Leu occurred in R plants. The results of in vitro ALS enzyme activity assays also supported that the extractable ALS from R plants were 23.22-fold resistant to mesosulfuron-methyl. In the light of the “R” resistance rating system, HN-14 has evolved RRR and RR resistance to fenoxaprop-P-ethyl, clodinafop-propargyl, haloxyfop-methyl, and fluazifop-P-butyl and R? (resistance may be developing) to pinoxaden, however remains sensitive to imazethapyr, quizalofop-P-ethyl, tralkoxydim, and isoproturon. These results indicated that the mesosulfuron-methyl resistance in the black-grass population HN-14 was driven by a target-site mechanism rather than a nontarget (at least P450s-mediated) mechanism. Full article

Alopecurus japonicus has been a serious weed across China and developed resistance to the acetyl-CoA carboxylase (ACCase)-inhibiting herbicide. The A. japonicus ACCase gene mutations accounting for target-site resistance (TSR) have been clarified, while non-target-site resistance (NTSR) is not distinct. Here, dose–response testing indicated that an A. japonicus population (R) was resistant to four ACCase-inhibiting herbicides fenoxaprop-P-ethyl, sethoxydim, clethodim, and pinoxaden. Compared with herbicide-susceptible A. japonicus (S), no known resistant mutations for TSR in ACCase were identified in the R population using sequencing. To investigate the NTSR mechanism, increased metabolism of fenoxaprop-P-ethyl was detected in the R population using high-performance liquid chromatography (HPLC) analysis. Notably, resistance cannot be reversed by P450 and GST inhibitors. RNA-seq was performed to further explore the resistance mechanisms, and eight candidate contigs (four glycosyl transferases (GT) and four ATP-binding cassette (ABC) transporters) were chosen and their expression patterns were validated using RT-qPCR. Three GT and three ABC transporter contigs were constitutively upregulated in the R population. In short, six contigs expressed highly in the R population causing enhanced fenoxaprop-P-ethyl metabolism appear to be involved in fenoxaprop-P-ethyl resistance. Full article

Echinochloa crus-galli var. zelayensis is a variant of E. crus-galli (L) Beauv, and it is the most pernicious weed in the east of China. Quinclorac, as synthetic auxin herbicide, could control this kind of weed effectively. In this study, two populations were used to further research the mechanism of quinclorac resistance, and the EcABCB1, EcABCB4 and EcABCB19 was functionally characterized to determine their roles in quinclorac resistance. It was found that root growth of quinclorac-resistant biotype SSXB-R was less inhibited by quinclorac at 5 μM and 50 μM when compared with the susceptible biotype JNNX-S. The results show that the IAA variations in root tip of JNNX-S were significantly higher than SSXB-R at 12 h after treatment with quinclorac (50 μM) and 1-N-naphthylthalamic acid (100 μM). There are no significant differences in IAA variations of the basal part of the root between susceptible and resistant biotypes after treatment with quinclorac and 1-N-naphthylthalamic acid (NPA). The transcript level of EcABCB1 and EcABCB19 in the root of JNNX-S showed down-regulated and up-regulated after treatment with quinclorac (TWQ) at 6 h in susceptible and resistant biotypes compared with control, respectively. The transcript level for EcABCB4 in the root showed up-regulated after TWQ at 12 h only in susceptible biotypes compared with control. It was found that the IC₅₀ to quinclorac of AtABCB4 and AtABCB19 mutants were significantly higher than the parent line Col-0. Full article

Halauxifen-methyl is a new auxin herbicide developed by Corteva Agriscience (Wilmington, DE, USA). It has been suggested that ABF5 may be the target of halauxifen-methyl, as AFB5 mutants of Arabidopsis thaliana are resistant to halauxifen-methyl, which preferentially binds to AFB5. However, the mode of action of halauxifen-methyl has not yet been reported. Therefore, the aim of the present study was to reveal the mode of action of halauxifen-methyl by exploring its influence on indole-3-acetic acid (IAA) homeostasis and the biosynthesis of ethylene and Abscisic Acid (ABA) in Galium aparine. The results showed that halauxifen-methyl could disrupt the homeostasis of IAA and stimulate the overproduction of ethylene and ABA by inducing the overexpression of the 1-aminocyclopropane-1-carboxylate synthase (ACS) and 9-cis-epoxycarotenoid dioxygenase (NCED) genes involved in ethylene and ABA biosynthesis, finally leading to senescence and plant death. Full article

With the expansion of saline-alkaline tolerant rice in China, the effects of salinity stress (NaCl) on quinclorac-resistant Echinochloa crus-galli (L.) Beauv (E. crus-galli) is unclear. In this study, the growth chamber experiment was conducted to test the germination and growth physiology of seven populations of E. crus-galli with quinclorac-different resistance levels which were collected from Hunan province. The results showed that a significant decrease of the germination rate and fresh weight of the plants, as well as the length of the roots and young shoots appeared, along with the increased resistance while treated with NaCl. However, no significant differences were detected between quinclorac-resistant and -susceptible E. crus-galli populations while without NaCl treatment. A further study with spectrophotometer showed that the salinity treatment resulted in the increase of the GST activity in all E. crus-galli populations, which are more obvious in those resistant biotypes, and transcriptomics revealed that salt stress reduces the adaptability of quinclorac-resistant E. crus-galli by reducing the biosynthesis, activities of antioxidant enzymes and metabolic enzyme. This study demonstrated that salinity stress (NaCl) may reduce the adaptability of quinclorac-resistant E. crus-galli. Full article

Large crabgrass, Digitaria sanguinalis (L.) Scop., is a devastating weed species in the cotton (Gossypium spp.) fields in China. It has developed resistance to haloxyfop-P-methyl, an aryloxyphenoxypropionate herbicide known for its ability to inhibit lipid synthesis and induce oxidative stress in weeds, due to years of continuous and intensive use. Here, we present the results from a nation-wide, long-term resistance monitoring effort. To understand the scale and level of haloxyfop-P-methyl resistance, a total of 65 D. sanguinalis populations from eight cotton production provinces, including Hunan, Jiangxi, Xinjiang, Henan, Hubei, Hebei, Shanxi, and Anhui, were collected from 2014–2017. Based on results from dose response to haloxyfop-P-methyl, we observed a gradient of sensitivity to haloxyfop-P-methyl among 65 field populations, ranging from sensitive (8), to low-level resistance (40; 2 ≤ RI ≤ 10) to moderate-level resistance (17; 10 < RI < 20). Although no high-level resistance (RI > 20) was found among the 65 populations, populations from Hunan and Hebei exhibited a rapid spread of field-evolved resistance. After challenged with haloxyfop-P-methyl (48.600 g a.i./ha at the 4–5-leaf stage), resistant and susceptible D. sanguinalis responded differently in the activity of an array of resistance-related enzymes, including acetyl-CoA carboxylase (ACCase), glutathione S-transferase (GSTs), nicotinamide-adenine dinucleotide phosphate (NADPH) and carboxylesterase (CarE), suggesting the potential involvement of NADPH, CarE and GSTs in D. sanguinalis to haloxyfop-P-methyl resistance. Full article

Herbicide safeners are a series of agrochemicals that can selectively protect crop plants from herbicide injury without affecting herbicidal efficacy. Understanding mechanisms by which safeners act is significant for discovery of novel types. Safeners primarily alleviate herbicide phytotoxicity to crop plants via several actions: (i) enhancing metabolism of herbicides in crops; (ii) affecting absorption and transportation of herbicides in crops; (iii) competitively binding to herbicide target sites; and (iv) affecting activity of target enzymes. This review describes recent advances in the action mechanisms of safeners, analyzes existing problems, anticipates the future direction of studies of modes of action of safeners, and prospects potential strategies to design safeners related to their reported mechanisms. The aim of this paper is to provide insight into mechanisms of safeners and give tips for development of new safeners. Full article

To date, effectively controlling resistant weeds has been a great challenge in modern agricultural production. Developing new modes of action of herbicides would be an efficient, convenient, and timely means of controlling resistant weeds. In particular, new modes of herbicide action do not appear to have evolutionary resistance or cross-resistance with existing herbicides. However, a few successful herbicides with new modes of action (MoAs) have been marketed in the past 20 years. In this paper, we analyzed limiting factors for the slow development of novel herbicide MoAs. We then summarized the positive herbicide targets for the herbicides that have been discovered in recent years, such as Solanyl Diphosphate Synthase (SPS), Fatty Acid Thioesterase (FAT), Plastid Peptide Deformylase (PDEF), and Dihydroxy-Acid Dehydratase (DHAD). Some commercial herbicide varieties have been obtained based on novel herbicide targets, such as Homogentisate Solanesyltransferase (HST) and Dihydroorotate Dehydrogenase (DHODH). This provides a new reference and idea for herbicide molecular design in the future. In addition, some practical and efficient methods were mentioned for the rational design, discovery, and development of targeted herbicides development. In order to overcome the adverse conditions of compound druggability, prodrug strategies are also used in herbicide development, which can optimize the administration, permeability, absorption, and distribution of the original drug molecule or a candidate compound and may provide more possibilities for the development of new herbicides. The development of new herbicides is fascinating, the challenges and rewards are great, and the path to success is becoming more apparent. Full article

The evolution of herbicide resistance in weeds has emerged as one of the most serious threats to sustainable food production systems, which necessitates the evaluation of herbicides to determine their efficacy. The first herbicide resistance case in the Iberian Peninsula was reported about 50 years ago, wherein Panicum dichotomiflorum was found to be resistant (R) to atrazine in Spanish maize fields. Since then, herbicide resistance has evolved in 33 weed species, representing a total of 77 single-herbicide-resistance cases in this geographic area: 66 in Spain and 11 in Portugal. Changes in agricultural practices, namely the adoption of non-tillage systems and the increased use of herbicides, led to the selection of weed biotypes resistant to a wide range of herbicides. Nowadays the most important crops in Spain and Portugal (maize, winter cereals, rice, citrus, fruits, and olive orchards) are affected, with biotypes resistant to several mechanisms of action (MoAs), namely: ALS inhibitors (20 species), ACCase inhibitors (8 species), PS II inhibitors (18 species), and synthetic auxin herbicides (3 species). More recently, the fast increase in cases of resistance to the EPSPS-inhibiting herbicide glyphosate has been remarkable, with 11 species already having evolved resistance in the last 10 years in the Iberian Peninsula. The diversity of resistance mechanisms, both target-site and non-target-site, are responsible for the resistance to different MoAs, involving point mutations in the target site and enhanced rates of herbicide detoxification, respectively. More serious are the 13 cases reported with multiple-herbicide resistance, with three cases of resistance to three–four MoAs, and one case of resistance to five MoAs. Future research perspectives should further study the relationship between management strategies and the occurrence of TSR and NTSR resistance, to improve their design, develop monitoring and diagnostic tools for herbicide resistance, and deepen the study of NTSR resistance. Full article