Resistance of Camelina microcarpa to acetolactate synthase inhibiting herbicides

An accession of Camelina microcarpa suspected to be resistant to sulfonylurea herbicides was identified in Oregon in 1998 field experiments. Greenhouse research confirmed that the putative resistant biotype was resistant to chlorsulfuron and metsulfuron on a whole plant level. Compared with the resistant (R) biotype, the susceptible (S) biotype was 1000 and 10 000‐fold more sensitive to metsulfuron and chlorsulfuron respectively. The R biotype was also resistant to other sulfonylurea, sulfonylaminocarbonyl‐triazolinone, imidazolinone and triazolopyrimidine herbicides. An in vivo enzyme assay indicated that acetolactate synthase (ALS) from the R plants required 111 times more chlorsulfuron to inhibit activity by 50% compared with the amount required to have a similar effect on ALS from S plants. Analysis of the nucleotide and amino acid sequences demonstrated that a single‐point mutation from G to T in the als1 gene conferred the change from the amino acid tryptophan to leucine at position 572 in the resistant biotype. This research confirmed that ALS inhibitor resistance in an Oregon accession of C. microcarpa is based on an altered target site conferred by a single‐point mutation.     

Point mutations including a novel Pro-197-Phe mutation confer cross-resistance to acetolactate synthase (ALS) inhibiting herbicides in Lactuca serriola in Australia

BACKGROUND

Control of prickly lettuce has become increasingly difficult for lentil growers in southern Australia because of widespread resistance to common herbicides, a lack of alternative herbicide options and the prolific production of highly mobile seed. This study aimed to quantify acetolactate synthase (ALS)-inhibiting herbicide resistance in the Mid North (MN) and Yorke Peninsula (YP) of South Australia, characterize the resistance mutations present and investigate population structure and gene flow in this species.

RESULTS

Resistance was identified in all populations tested, with average survival of 92% to chlorsulfuron and 95% to imazamox + imazapyr. Five different amino acid substitutions were identified at proline 197 of the ALS gene. There was no significant difference in the median lethal dose (LD₅₀) between plants with these five different substitutions when treated with metsulfuron-methyl; however, the imidazolinone resistance level was higher in plants with a phenylalanine substitution and lower in plants with a serine. Population structure based on 701 single nucleotide polymorphisms and 271 individuals provided evidence for both independent evolution of the same mutation in different populations, as well as frequent short- to medium-distance dispersal accompanied by occasional long-distance dispersal events. The overall inbreeding coefficient (F_IS) was calculated at 0.5174, indicating an intermediate level of outcrossing despite the cross-pollination experiment showing only low outcrossing. In the structure analyses, most individuals from YP were assigned to a single cluster, whereas most individuals from MN were assigned 50% to each of two clusters, indicating some genetic differences between these two regions, but also evidence for dispersal between them.

CONCLUSIONS

Use of imidazolinone herbicides has selected for mutations conferring higher levels of resistance, such as the Pro-197-Phe mutation, and resulted in further spread of resistance in this species. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Response of an acetolactate synthase (ALS)-resistant biotype of Amaranthus rudis to selected ALS-inhibiting and alternative herbicides

An Amaranthus rudis Saner (common water-hemp) biotype from a field treated for two consecutive years with a mixture of chlorimuron and metribuzin was tested in greenhouse and laboratory studies to assess resistance and cross-resistance to four acetolactale synthase (ALS)-inhibiting herbicides. The biotype demonstrated >1920-fold resistance at the whole plant level, and >850-fold resistance at the ALS enzyme to chlorimuron, compared with a susceptible biotype. This chlorimuron-resistant biotype was also cross-resistant to primisuifu-ron, haiosulfuron and imazethapyr. In greenhouse studies, atrazine alone or in combination with ALS-inhibiting herbicides provided excellent control of the resistant biotype of A. rudis . Combinations of dicamba and ALS-inhibitors also provided adequate control. Additionally, premixtures of flumetsulam and metolachlor and of dicamba and atrazine furnished excellent control of this chlorimuron-resistant A. rudis biotype.     

Occurrence,resistance factors and cross-resistance patterns to herbicides inhibiting acetolactate synthase (ALS) of Echinochloa crus-galli (L.) Pal. Beauv. in Central Europe

Journal of Plant Diseases and Protection - Echinochloa crus-galli (L.) Pal. Beauv. is one of the most noxious weeds in maize cultivation and has evolved target-site resistance to ALS-inhibiting...     

Transformation a mutant Monochoria vaginalis acetolactate synthase (ALS) gene renders Arabidopsis thaliana resistant to ALS inhibitors

Acetolactate synthase (ALS) genes from Monochoria vaginalis resistant (R) and susceptible (S) biotypes against ALS inhibitors found in Korea revealed a single amino acid substitution of Proline (CCT), at 169th position based on the M. vaginalis ALS sequence numbering, to serine (TCT) in conserved domain A of the gene (equal to the proline 197 in Arabidopsis thaliana ALS gene sequence). A. thaliana plants transformed with the single mutated (Pro₁₆₉ to Ser) M. vaginalis ALS gene (including transit signal peptide) showed cross-resistance patterns to ALS-inhibiting herbicides, like as sulfonylurea-herbicide bensulfuron methyl (R/S factor of 9.5), imidazolinone-herbicide imazapyr (R/S factor of 5.1), and triazolopyrimidine-herbicide flumetsulam (R/S factor of 17.6) when measuring hypocotyls’ length of A. thaliana. The ALS activity from the transgenic A. thaliana plants confirmed the cross-resistance pattern to these herbicides like as R/S factor of 8.3 to bensulfuron methyl, 2.3 to imazapyr, and 13.2 to flumetsulam.     

Cross‐resistance of Echinochloa species to acetolactate synthase inhibitor herbicides

This study was conducted to evaluate the cross‐resistance of acetolactate synthase (ALS) inhibitors with different chemistries, specifically azimsulfuron (sulfonylurea), penoxsulam (triazolopyrimidine sulfonanilide) and bispyribac‐sodium (pyrimidinyl thio benzoate), in Echinochloa oryzicola and Echinochloa crus‐galli that had been collected in South Korea and to investigate their herbicide resistance mechanism. Both Echinochloa spp. showed cross‐resistance to the ALS inhibitors belonging to the above three different chemistries. In a whole plant assay with herbicides alone, the resistant/susceptible ratios for azimsulfuron, penoxsulam and bispyribac‐sodium were 12.6, 28.1 and 1.9 in E. oryzicola and 21.1, 13.7 and 1.8 in E. crus‐galli, respectively. An in vitro ALS enzyme assay with herbicides showed that the I ₅₀‐values of the resistant accessions were approximately two‐to‐three times higher than the susceptible accessions, with no statistical difference, suggesting that the difference in ALS sensitivity cannot explain ALS inhibitor resistance in Echinochloa spp. for azimsulfuron, penoxsulam and bispyribac‐sodium. A whole plant assay with fenitrothion showed that the GR ₅₀‐values significantly decreased in both the resistant E. oryzicola and E. crus‐galli accessions when azimsulfuron, penoxsulam and bispyribac‐sodium were applied with the P450 inhibitor, while no significant decrease was observed in the susceptible accessions when the P450 inhibitor was used. Thus, these results suggest that ALS inhibitor cross‐resistance for azimsulfuron, penoxsulam and bispyribac‐sodium is related to enhanced herbicide metabolism.     

非转基因抗除草剂玉米对三种乙酰乳酸合成酶抑制剂类除草剂的田间抗性表现

为评估中国农业大学培育的非转基因抗除草剂玉米品系958R和335R在大田条件下对乙酰乳酸合成酶（acetolactate synthase,ALS）抑制剂类除草剂的抗性表现,利用甲咪唑烟酸、砜嘧磺隆、唑嘧磺草胺3种除草剂对郑单958、958R、先玉335、335R共4种玉米杂交种进行了播后苗前土壤处理,每种除草剂设3个处理剂量（1、3、9倍推荐剂量）,并于施药2周和4周后进行株高测定,于收获晾干后测产。结果表明,在甲咪唑烟酸216、648 g（a.i.）/hm²处理下,郑单958和先玉335均已绝产,而958R和335R产量均未受影响;在砜嘧磺隆或唑嘧磺草胺高剂量处理下,常规玉米品种郑单958和先玉335株高的最高降幅分别为25.7%和35.2%,田间药害反应显著,而958R和335R则抗性反应显著。研究表明,非转基因抗除草剂玉米杂交种具有良好的田间抗性,不仅能有效解决玉米田砜嘧磺隆和唑嘧磺草胺等ALS除草剂的药害问题,还能够通过引入甲咪唑烟酸等新的ALS除草剂更好地防除玉米田的杂草。     

Assessment of acetolactate synthase (ALS) tolerance to imazethapyr in red rice ecotypes (Oryza spp) and imidazolinone tolerant/ resistant rice (Oryza sativa) varieties

Three red rice ecotypes (Oryza spp), including LA 5, MS 5 and TX 4, were evaluated for acetolactate synthase resistance/tolerance to imazethapyr. The red rice ecotypes were compared with a tolerant line (CL-121), a resistant line (CL-161) and a conventional rice variety (Cypress). Based on enzymatic activity, the mean I(50) values were 1.5, 1.1, 1.5, 1.6, 20.8 and 590.6 microM imazethapyr, respectively, for LA 5, MS 5, TX 4, Cypress, CL-121 and CL-161. CL-161 was 32 times more resistant than CL-121 and at least 420 times more resistant than the average of the red rice ecotypes and Cypress. Results from the acetolactate synthase (ALS) assay showed that red rice ecotypes and Cypress had high susceptibility to imazethapyr when compared with the tolerant CL-121 and the resistant CL-161. Measurable enzymatic tolerance to ALS-inhibiting herbicides has not yet developed in these red rice ecotypes.     

Detection of resistance to acetolactate synthase inhibitors in weeds with emphasis on DNA-based techniques: a review

Resistance to herbicides inhibiting acetolactate synthase (ALS) has been increasing at a faster rate than in any other herbicide group. The great majority of these cases are due to various single-nucleotide polymorphisms in the ALS gene endowing target site resistance. Many diagnostic techniques have been devised in order to confirm resistance and help producers to adopt the best management strategies. Recent advances in DNA technologies coupled with the knowledge of sequence information have allowed the development of accurate and rapid diagnostic tests. While whole plant-based diagnostic techniques such as seedling bioassays or enzyme-based in vitro bioassays provide accurate results, they tend to be labour- and/or space-intensive and will only respond to the particular herbicides tested, making resolution of cross-resistance patterns more difficult. Successful DNA-based diagnosis of ALS inhibitor resistance has been achieved with three main techniques, (1) restriction fragment length polymorphism, (2) polymerase chain reaction amplification of specific alleles and (3) denaturing high-performance liquid chromatography. All DNA-based techniques are relatively rapid and provide clear identification of the mutations causing resistance. Resistance based on non-target mechanisms is not identified by these DNA-based methods; however, given the prevalence of target site-based ALS inhibitor resistance, this is a minor inconvenience.     

荠菜对乙酰乳酸合成酶抑制剂类除草剂的抗性水平及其分子机制

为明确荠菜种群对苯磺隆的抗性水平及其靶标抗性产生的分子机制,采用整株水平测定法测定了荠菜对苯磺隆及其他5种乙酰乳酸合成酶（ALS）抑制剂类除草剂的抗性水平,同时扩增和比对了荠菜抗性和敏感种群之间ALS基因的差异。结果显示:与敏感种群15-ZMD-1相比,抗性种群15-ZMD-5对苯磺隆产生了高水平抗性,抗性倍数为219.6;15-ZMD-5种群不同单株中共存在3种突变方式,分别为ALS基因197位点脯氨酸（CCT）突变为亮氨酸（CTT）、574位点色氨酸（TGG）突变为亮氨酸（TTG）以及单株同时发生上述197和574位点的氨基酸突变。15-ZMD-5抗苯磺隆种群对嘧草硫醚、啶磺草胺和氟唑磺隆均产生了高水平的交互抗性,抗性倍数分别为41.2、79.3和87.8;对双氟磺草胺和咪唑乙烟酸产生了低水平的交互抗性,抗性倍数分别为8.5和5.6。分析表明,荠菜抗性种群ALS基因发生的氨基酸突变可能是导致其对ALS抑制剂类除草剂产生抗性的重要原因之一。     

A molecular assay for the proactive detection of target site-based resistance to herbicides inhibiting acetolactate synthase in Alopecurus myosuroides

Acetolactate synthase (ALS) inhibitors are the most resistance‐prone herbicide group. Rapid resistance diagnosis is thus of importance for their optimal use. We formulate rules to use the derived cleaved amplified polymorphic sequence method to develop molecular tools detecting a change at a given codon, the nature of which is unknown. We applied them to Alopecurus myosuroides (black grass) to develop assays targeting ALS codons A122, P197, A205, W574 and S653 that are crucial for herbicide sensitivity. These assays detected W574L or P197T, or both substitutions, in most plants analysed from a field where ALS inhibitors failed after 3 years of use. Similar assays can easily be set up for any species. Given the rapidity of selection for resistance to ALS inhibitors, these assays should be very useful in proactive herbicide resistance diagnosis.     

耳叶水苋对乙酰乳酸合成酶抑制剂的抗性及其分子机制初探

近年来长江下游地区稻田耳叶水苋Ammannia arenaria H.B.K.危害十分严重。采用盆栽法首次测定了耳叶水苋对苄嘧磺隆等药剂的抗性水平,同时分析了其抗性和敏感种群间乙酰乳酸合成酶(ALS)基因的DNA序列及其RNA表达差异。结果表明:采自浙江嘉兴(JX110)、江苏苏州(JS039)、浙江宁波(NB0143-05)和安徽广德(AH014)的耳叶水苋生物型对苄嘧磺隆的抗性指数(RI)分别为67.90、17.59、44.63和8.37,对苄嘧磺隆表现出中高水平抗性的生物型对五氟磺草胺、双草醚及咪唑乙烟酸也产生了低水平的抗性。获得了耳叶水苋ALS基因全长核苷酸序列2235 bp,编码667个氨基酸,仅发现NB0143-05等3种抗性生物型ALS酶的氨基酸序列非保守区第93位的亮氨酸被脯氨酸取代。然而,NB0143-05的ALS酶对ALS抑制剂的敏感性大幅度降低(RI 37.04),且在苄嘧磺隆处理后4 d的ALS基因表达量是敏感生物型(HZ001)的1.86倍。这表明,ALS酶对药剂的敏感性降低以及被苄嘧磺隆诱导后ALS基因表达量显著增加,很可能是耳叶水苋生物型NB0143-05对ALS抑制剂产生抗性的原因。     

除草剂防除马尼拉草坪杂草试验

草坪宁1号7g/666.7m^2药后35d,60d的总体防效分别为90．8％和70．5％，明显高于阿特拉津100ml 都尔80ml/666.7m^2和阿特拉津100ml 乙草胺80ml/666.7m^2 2处理，对马尼拉草坪安全，值得推广。