Explore the vast range of titles available.

The worldwide contamination of waters and food by herbicides is a major health issue, yet the toxic effects of herbicides to non-target organisms and ecosystems have been poorly summarized. Here we review the effects of herbicides belonging to the groups of chloroacetanilides, imidazolinones, sulfonylureas, and pyrimidinylcarboxylic, on small invertebrates, high vertebrates, plants, and the surrounding ecosystems. We describe toxicity in terms of behavioural changes, molecular biosynthesis, endocrine disruption, immunological responses, enzymatic alteration, and reproductive disorders. Strategies to decrease toxic effects are also presented. We observe widespread toxicity threats in amphibians and major aquatic species. Each herbicide group displays a different toxicity risk. For instance, chloroacetanilides display higher risks to soil, aquatic, algal, cyanobacteria, and terrestrial species, whereas alachlor, acetochlor, and metolachlor are highly carcinogenic to humans. Most imidazolinone herbicides cause phytotoxicity in non-target and succeeding crops. Sulfonyl-urea herbicides are severely toxic to soil microbes and succeeding crops. Pyrimidinylcarboxy herbicides are more toxic to soil microbes, aquatic species, and rats.

Pre-emergence herbicide herbicides are an efficient way to manage weeds in wheat and could control Italian ryegrass and wild radish. We assess control of these weeds by PRE herbicides applied after crop sowing, as well as determining their phytotoxicity to imidazolinone resistant Clearfield® (CL) wheat. All trials involved testing of different PRE herbicides applied right after wheat sowing. Field trials were conducted in 2021 in two sites (Santo Angelo and Santa Maria), both sown with cv. TBIO Ello CL. Soils were classified as oxisol (53% clay) and ultisol (31% clay), respectively. In all trials, variables evaluated included visual assessments of injuries, number of plants, and weed control levels. Crop yield components were also determined in field experiments, whereas variables related to weed densities were assessed in trials. Clomazone, sulfentrazone, and quinclorac herbicides were not selective to wheat. Imidazolinones herbicides were shown to be selective, and a premix formulation containing imazapyr+imazapic allowed for broad-spectrum weed control, treatments containing PPO-inhibiting herbicides were the most effective for wild radish.

Resistance of agricultural crops to herbicides is an important topic that concerns many researchers. One of the most popular groups of herbicides is the imidazolinone group. Resistant forms of crops such as wheat (Triticum aestivum L.), sunflower (Helianthus annuus L.), corn (Zea mays L.), rice (Oryza sativa L.) and oilseed rape (Brassica napus L.) have been developed to this group of herbicides. All crops resistant to this group of herbicides have the commercial name Clearfield®. In this review, the information concerning oilseed rape resistance to the imidazolinone group of herbicides is collected and summarized; it will be useful for breeders and researchers engaged in this direction. This review touches upon the topic of mechanisms of oilseed rape resistance to imidazolinones. Mutation variants known to date, which provide resistance to this group of herbicides, are described, and known molecular markers of them are presented. Approaches to the selection of oilseed rape for resistance to the imidazolinone group of herbicides are mentioned. Various methods of utilizing imidazolinone resistance to improve the purity of hybrid seeds are also considered.

Chickpea (Cicer arietinum L.) is an important crop in crop-rotation management in Israel. Imidazolinone herbicides have a wide spectrum of weed control, but chickpea plants are sensitive to acetohydroxyacid synthase (AHAS; also known as acetolactate synthase [ALS]) inhibitors. Using the chemical mutagen ethyl methanesulfonate (EMS), we developed a chickpea line (M2033) that is resistant to imidazolinone herbicides. A point mutation was detected in one of the two genes encoding the AHAS catalytic subunit of M2033. The transition of threonine to isoleucine at position 192 (203 according to Arabidopsis) conferred resistance of M2033 to imidazolinones, but not to other groups of AHAS inhibitors. The role of this substitution in the resistance of line M2033 was proven by genetic transformation of tobacco plants. This resistance showed a single-gene semidominant inheritance pattern. Conclusion: A novel mutation, T192I (T203I according to Arabidopsis), providing resistance to IMI herbicides but not to other groups of AHAS inhibitors, is described in the AHAS1 protein of EMS-mutagenized chickpea line M2033.

Japanese foxtail (Alopecurus japonicus Steud.) is an invasive grass weed that severely threatens the production of wheat (Triticum aestivum L.) and canola (Brassica napus L.) crops in eastern Asia. Mesosulfuron-methyl is a highly efficient acetolactate synthase (ALS)-inhibiting herbicide widely used for control of this species in China. However, in recent years, some A. japonicus populations have evolved resistance to mesosulfuron-methyl by different amino acid substitutions (AASs) within the ALS gene. In the current study, 11 populations of A. japonicus were collected from Anhui Province, China, where the wheat fields were severely infested with this weed. Based on single-dose screening, eight of these populations evolved resistance to mesosulfuron-methyl, and gene sequencing revealed three AASs located in codon 197 or 574 of the ALS gene in the different resistant populations. Subsequently, three typical populations, AH-1, AH-4, and AH-10 with Trp-574-Leu, Pro-197-Thr, and Pro-197-Ser mutations, respectively, in ALS genes were selected to characterize their cross-resistance patterns to ALS inhibitors. Compared with the susceptible population AH-S, AH-1 showed broad-spectrum cross-resistance to sulfonylureas (SUs), imidazolinones (IMIs), triazolopyrimidines (TPs), and sulfonyl-aminocarbonyl-triazolinones (SCTs); whereas AH-4 and AH-10 were resistant to SUs, TPs, and SCTs but sensitive to IMIs. Moreover, all three resistant populations were sensitive to both photosystem II inhibitor isoproturon and 4-hydroxyphenylpyruvate dioxygenase inhibitor QYM201 (1-(2-chloro-3-(3-cyclopropyl-5-hydroxy-1-methyl-1H-pyrazole-4-carbonyl)-6-(trifluoromethyl)phenyl)piperidin-2-one). Based on the current state of knowledge, this study is the first report of A. japonicus evolving cross-resistance to ALS-inhibiting herbicides due to a Pro-197-Ser mutation in the ALS gene.

Rice is an important crop and a staple food in Malaysia. Herbicides are used extensively to control weeds, which represent a major constraint to yield production. Although the introduction of Imidazolinone-resistant Rice with its management system (IRPS) has greatly improved both yields and weed control, the system is designed to be used for only a short term before transitioning to local varieties. Thus, a survey was conducted among 115 farmers to obtain information on their general knowledge on weed control and IRPS. The results showed that the majority of the farmers use herbicides to control all types of weed presented, with a small minority still using manual control. The majority of farmers using IRPS were applying the herbicide imidazolinone when soil condition were right, and only once per season, which is the recommendation. Most of the farmers still utilized imidazolinone to control weedy rice but would not use it on other weeds. However, many of the farmers perceived imidazolinone as becoming more ineffective and expensive and were willing to change to other herbicides if there was a viable alternative. Although herbicide is the main method employed in controlling weeds when using IRPS, farmers still regard imidazolinone as an ineffective herbicide. The reason IRPS is still in use is due to the high yields provided. This study shows a better understanding of knowledge on weeds and IRPS among farmers. Nonetheless, the IRPS will become a redundant system due to the ineffectiveness of imidazolinone and a new system should be introduced to replace it.

Induced mutagenesis can be an effective way to increase variability in self-pollinated crops for a wide variety of agronomically important traits. Crop resistance to a given herbicide can be of practical value to control weeds with efficient chemical use. In some crops (for example, wheat, maize, and canola), resistance to imidazolinone herbicides (IMIs) has been introduced through mutation breeding and is extensively used commercially. However, this production system imposes plant-back restrictions on rotational crops because of herbicide residuals in the soil. In the case of barley, a preferred rotational crop after wheat, a period of 9–18 mo is required. Thus, introduction of barley varieties showing resistance to IMIs will provide greater flexibility as a rotational crop. The objective of the research reported was to identify resistance in barley for IMIs through induced mutagenesis. To achieve this objective, a sodium azide-treated M₂/M₃ population of barley cultivar Bob was screened for resistance against acetohydroxy acid synthase (AHAS)-inhibiting herbicides. The phenotypic screening allowed identification of a mutant line showing resistance against IMIs. Molecular analysis identified a single-point mutation leading to a serine 653 to asparagine amino acid substitution in the herbicide-binding site of the barley AHAS gene. The transcription pattern of the AHAS gene in the mutant (Ser653Asn) and WT has been analyzed, and greater than fourfold difference in transcript abundance was observed. Phenotypic characteristics of the mutant line are promising and provide the base for the release of IMI-resistant barley cultivar(s).

Recently, farmers in Brazil have observed a decline in efficacy of glyphosate, chlorimuron, and imazethapyr control of smooth pigweed (Amaranthus hybridus L.). The objectives of this study were to quantify the resistance of Amaranthus in Brazil to glyphosate and acetolactate synthase (ALS)-inhibiting herbicides, elucidate the mechanism of resistance, and assess the frequency of shifts in sensitivity to glyphosate and chlorimuron in Brazil. Dose–response assays were conducted in a greenhouse with glyphosate, chlorimuron, and imazethapyr. This was followed by sequencing of the EPSPS and ALS genes. Additionally, 740 Amaranthus populations across several Brazilian states were monitored over 4 yr, subjected to a single discriminatory dose of glyphosate and chlorimuron. The populations BR18Asp051 and BR21Asp205 were resistant to glyphosate, chlorimuron, and imazethapyr. The elevated resistance level to glyphosate in these populations is attributed to multiple amino acid substitutions (TAP-IVS) in the EPSPS gene; and cross-resistance to sulfonylureas and imidazolinones is conferred by the Trp-574-Leu substitution in the ALS gene in both populations. Overall, resistance distribution indicated that 88% of the sampled populations were considered sensitive to glyphosate, while 66% were sensitive to chlorimuron. Furthermore, 10% of the samples demonstrated multiple resistance to both active ingredients. A shift in glyphosate sensitivity was observed in four states in Brazil; however, sensitivity shifts to chlorimuron were more widely dispersed in Brazilian agricultural regions.

Wild mustard (Sinapis arvensis L.) is a weed that frequently infests winter wheat (Triticum aestivum L.) fields in Golestan province, Iran. Tribenuron-methyl (TM) has been used recurrently to control this species, thus selecting for resistant S. arvensis populations. The objectives were: (1) to determine the resistance level to TM of 14 putatively resistant (PR) S. arvensis populations, collected from winter wheat fields in Golestan province, Iran, in comparison to one susceptible (S) population; and (2) to characterize the resistance mechanisms and the potential evolution of cross-resistance to other classes of acetolactate synthase (ALS)-inhibiting herbicides in three populations (AL-3, G-5, and Ag-Sr) confirmed as being resistant (R) to TM. The TM doses required to reduce the dry weight of the PR populations by 50% were between 2.2 and 16.8 times higher than those needed for S plants. The ALS enzyme activity assays revealed that the AL-3, G-5, and Ag-Sr populations evolved cross-resistance to the candidate ALS-inhibiting herbicides from the sulfonylureas (SU), triazolopyrimidines (TP), pyrimidinyl-thiobenzoates (PTB), sulfonyl-aminocarbonyl-triazolinone (SCT), and imidazolinones (IMI) classes. No differences in absorption, translocation, or metabolism of [14C]TM between R and S plants were observed, suggesting that these non-target mechanisms were not responsible for the resistance. The ALS gene of the R populations contained the Trp-574-Leu mutation, conferring cross-resistance to the SU, SCT, PTB, TP, and IMI classes. The Trp-574-Leu mutation in the ALS gene conferred cross-resistance to ALS-inhibiting herbicides in S. arvensis from winter wheat fields in Golestan province. This is the first TM resistance case confirmed in this species in Iran.