Characterisation of target-site resistance to ACCase-inhibiting herbicides in the weed Alopecurus myosuroides (black-grass)

Resistance to aryloxyphenoxypropionate (AOPP), cyclohexanedione (CHD) and phenylurea herbicides was determined in UK populations of Alopecurus myosuroides Huds. Two populations (Oxford AA1, Notts. A1) were highly resistant (Resistance indices 13-->1000) to the AOPP and CHD herbicides fenoxaprop, diclofop, fluazifop-P and sethoxydim, but only marginally resistant to the phenylurea, chlorotoluron. Analyses of acetyl coenzyme A carboxylase (ACCase) activity showed that an insensitive ACCase conferred resistance to all the AOPP/CHD herbicides investigated. Another population, Oxford S1, showed no resistance to sethoxydim at the population level, but contained a small proportion of plants (<10%) with an insensitive ACCase. Genetic studies on the Notts A1 and Oxford S1 populations demonstrated that target site resistance conferred by an insensitive ACCase is monogenic, nuclearly inherited with the resistant allele showing complete dominance. Investigations of the molecular basis of resistance in the Notts A1 population showed that sethoxydim resistance in A myosuroides was associated with the substitution of an isoleucine in susceptible with a leucine in resistant plants, which has also been found in three other resistant grass-weed species (Setaria viridis (L) Beauv, Avena fatua L, Lolium rigidum Gaud).     

Differences in the molecular basis of resistance to the cyclohexanedione herbicide sethoxydim in Lolium multiflorum

Resistance to the cyclohexanedione (CHD) herbicide sethoxydim was investigated in two UK Lolium multiflorum populations, Yorks A2 and PYL. Resistance screening experiments demonstrated a qualitative difference in the responses of the two populations to sethoxydim, suggesting that the molecular basis of resistance between them was different. After treatment, Yorks A2 plants were either alive (78% of sample tested) or dead (22% tested) but plants of the PYL population showed two further intermediate categories of response. The level of acetyl-CoA carboxylase (ACCase) insensitivity directly correlated with the degree of resistance at the whole plant level, indicating that the molecular basis of resistance is associated with differences in ACCase sensitivity in each population. Direct sequencing of the carboxyl transferase domain of the ACCase gene showed that an Ile-418-Leu substitution in the L. multiflorum chloroplastic ACCase (GenBank accession number AY710293 ) confers resistance to sethoxydim in Yorks A2. This corresponds to amino acid residue 1781 in the Alopecurus myosuroides full ACCase sequence. This is the first report of this mutation in this L. multiflorum, which has also been reported in four other grass-weeds, including L. rigidum. However, no amino acid substitutions were found to be specifically associated with the resistant phenotypes in the PYL population and the molecular basis of resistance in this population remains to be resolved.     

Resistance to diclofop-methyl in two Lolium spp. populations from Italy: studies on the mechanism of resistance

The mechanisms of herbicide resistance were investigated in two diclofop-methyl-resistant Lolium spp. populations from central Italy, Roma '94 and Tuscania '97. These two populations were compared with two susceptible Italian populations (Vetralla '94, Tarquinia '97) and a resistant and a susceptible population from Australia, SLR31 and VLR1. The activity of acetyl Co-A carboxylase (ACCase) extracted from susceptible (S) or resistant (R) individuals from the Italian populations was inhibited by both aryloxyphenoxypropanoate (diclofop acid and fluazifop acid) and cyclohexanedione (sethoxydim) herbicides. Diclofop-methyl was rapidly de-esterified to diclofop acid at a similar rate in both R and S populations. In all populations, diclofop acid was subsequently degraded to other metabolites. The rate of degradation of diclofop acid was not significantly faster in R than in S populations; however, diclofop acid was degraded more completely in Roma '94 and Tuscania '97 compared with the S populations. Application of the mixed-function oxidase inhibitor 1-aminobenzotriazole (ABT) significantly enhanced diclofop-methyl toxicity towards both R populations, but not in S populations. However, enhanced herbicide metabolism does not completely account for the measured resistance level. A mechanism other than an altered ACCase and enhanced herbicide metabolism appears to be responsible for resistance to diclofop-methyl in Roma '94 and Tuscania '97.     

An aspartate to glycine change in the carboxyl transferase domain of acetyl CoA carboxylase and non‐target‐site mechanism(s) confer resistance to ACCase inhibitor herbicides in a Lolium multiflorum population

BACKGROUND: The increasing use of ACCase‐inhibiting herbicides has resulted in evolved resistance in key grass weeds infesting cereal cropping systems worldwide. Here, a thorough and systematic approach is proposed to elucidate the basis of resistance to three ACCase herbicides in a Lolium multiflorum Lam. (Italian rye grass) population from the United Kingdom (UK24). RESULTS: Resistance to sethoxydim and pinoxaden was always associated with a dominant D2078G (Alopecurus myosuroides Huds. equivalent) target‐site mutation in UK24. Conversely, whole‐plant herbicide assays on predetermined ACCase genotypes showed very high levels of resistance to diclofop‐methyl for all three wild DD2078 and mutant DG2078 and GG2078 ACCase genotypes from the mixed resistant population UK24. This indicates the presence of other diclofop‐methyl‐specific resistance mechanism(s) yet to be determined in this population. The D2078G mutation could be detected using an unambiguous DNA‐based dCAPS procedure that proved very transferable to A. myosuroides, Avena fatua L., Setaria viridis (L.) Beauv. and Phalaris minor Retz. CONCLUSION: This study provides further understanding of the molecular basis of resistance to ACCase inhibitor herbicides in a Lolium population and a widely applicable PCR‐based method for monitoring the D2078G target‐site resistance mutation in five major grass weed species. Copyright © 2010 Society of Chemical Industry     

Biochemical mechanisms of cross-resistance to aryloxyphenoxypropionate and cyclohexanedione herbicides in populations of Avena spp.

Aryloxyphenoxypropionate (APP) and cyclohexanedione (CHD) herbicides are used extensively in the UK to control grass weeds, including Avena spp. (wild-oats). Reports of resistance to APP and CHD herbicides are a particular concern for the agricultural community. In this study, the responses of four UK Avena populations were characterized towards the APP herbicides fenoxaprop-P-ethyl and fluazifop-P-butyl, and towards the CHD herbicides cycloxydim and tralkoxydim. An A. sterilis ssp. ludoviciana population (T/41) was found to be highly resistant to fenoxaprop-P-ethyl and fluazifop-P-butyl, but did not show cross-resistance to cycloxydim and tralkoxydim. In contrast, one A. sterilis ssp. ludoviciana (T/11) and one A. fatua population (Dorset) showed partial resistance to both APP herbicides and also showed cross-resistance to the CHD herbicide tralkoxydim, but not to cycloxydim. Before this study, the biochemical mechanisms that confer resistance to the APP and CHD herbicides in UK Avena populations were unknown. Results from the present study show that an enhanced rate of metabolism of fenoxaprop-P-ethyl was found to confer resistance in the two partially resistant Avena populations (T/11 and Dorset), and the presence of an insensitive form of the target enzyme, ACCase, was responsible for target site resistance to fenoxaprop-P-ethyl and fluazifop-P-butyl in the highly resistant population T/41. Cross-resistance to the CHD herbicide tralkoxydim in the T/11 and Dorset populations was not conferred by insensitive ACCase, and was most probably caused by enhanced metabolism. This is the first report that resistance to fenoxaprop-P-ethyl can be conferred by enhanced metabolism in Avena spp.     

Diclofop‐resistant Lolium rigidum from northern Greece with cross‐resistance to ACCase inhibitors and multiple resistance to chlorsulfuron

Repeated use of ACCase‐ and ALS‐inhibiting herbicides in northern Greece has resulted in the evolution of a population of Lolium rigidum resistant to diclofop and chlorsulfuron. The biotype from Athos was highly resistant to diclofop and also exhibited differential cross‐resistance to clodinafop, fluazifop, tralkoxydim and sethoxydim. Assay of ACCase activity confirmed that the resistant biotype was tenfold more resistant to diclofop than the susceptible biotype, suggesting that the resistance mechanism could involve an altered target site. The diclofop‐resistant biotype has also exhibited multiple resistance to chlorsulfuron and the mechanism for this is unknown. Seed‐bioassay was found to be a rapid, cheap and reliable method to identify populations of L rigidum resistant to ACCase inhibitors and chlorsulfuron. Moreover, root elongation in the seed bioassay was more sensitive to ACCase inhibitors and chlorsulfuron than shoot elongation. © 2000 Society of Chemical Industry     

Cross-resistance profile of mesosulfuron-methyl-resistant Italian ryegrass in the southern United States

Diclofop-resistant Lolium species (ryegrass) is a major weed problem in wheat production worldwide. This study was conducted to determine the resistance pattern of diclofop-resistant ryegrass accessions from the southern United States to mesosulfuron-methyl, a recently commercialized herbicide for ryegrass control in wheat; to determine the cross-resistance pattern of a Lolium multiflorum Lam. (Italian ryegrass) accession, 03-1, to acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibitors; and to determine the resistance mechanism of Italian ryegrass to mesosulfuron-methyl. Seventeen ryegrass accessions from Arkansas and Louisiana, including standard resistant and susceptible accessions, were used in this experiment. Fourteen of the 17 accessions were more resistant (four- to > 308-fold) to diclofop than the standard susceptible biotype. One accession, 03-1, was resistant to mesosulfuron-methyl as well as to other ALS inhibitor herbicides such as chlorsulfuron, imazamox and sulfometuron. Accession 03-1, however, did not show multiple resistance to the ACCase inhibitor herbicides diclofop, fluazifop, clethodim, sethoxydim and pinoxaden, nor to glyphosate. The in vivo ALS activity of the 03-1 biotype was less affected by mesosulfuron-methyl than the susceptible biotype. This indicates that the resistance mechanism of Italian ryegrass to mesosulfuron-methyl is partly due to an alteration in the target enzyme, ALS. It is concluded that diclofop-resistant ryegrass in the southern United States can be generally controlled by mesosulfuron-methyl. However, mesosulfuron-methyl must be used with caution because not all ryegrass populations are susceptible to it. There is a need for more thorough profiling of ryegrass resistance to herbicides.     

Confirmed resistance to aryloxyphenoxypropionate herbicides in Phalaris minor populations in Iran

Phalaris minor (littleseed canary grass) is a major weed in wheat fields in some parts of Iran. Diclofop‐methyl, fenoxaprop‐P‐ethyl, and clodinafop‐propargyl are three acetyl coenzyme A carboxylase (ACCase)‐inhibiting herbicides that are commonly used to control this grass in wheat fields. Thirty‐four P. minor populations with suspected resistance to ACCase‐inhibiting herbicides were sampled from wheat fields in the provinces of Fars and Golestan in Iran. The dose–response assays that were conducted under controlled greenhouse conditions indicated that 14 populations were resistant to fenoxaprop‐P‐ethyl, seven populations were resistant to both fenoxaprop‐P‐ethyl and diclofop‐methyl, and three populations were resistant to fenoxaprop‐P‐ethyl, diclofop‐methyl, and clodinafop‐propargyl. These populations showed different levels of resistance to the applied herbicides, compared to the susceptible population. These results suggest that different mechanisms of resistance could be involved. The enzyme assay revealed that the existence of modified ACCase in the three most‐resistant populations (AR, MR4, and SR3) is responsible for the resistance of these populations.     

A Diclofop-methyl-Resistant Avena sterilis Biotype with a Herbicide-Resistant Acetyl-coenzyme A Carboxylase and Enhanced Metabolism of Diclofop-methyl

An Avena sterilis biotype was found to be highly resistant to aryloxyphenoxypropionate (APP) herbicides, especially diclofop-methyl. At the enzyme level, this biotype contained a modified acetyl-coenzyme A carboxylase (ACCase) with six-fold resistance to diclofop acid. Absorption and translocation of [¹⁴C]diclofop-methyl applied to the leaf axil of the two-leaf stage plants were similar in both susceptible and resistant biotypes. However, the rate of metabolism of [¹⁴C]diclofop was increased 1·5-fold in this resistant biotype compared to the susceptible. Experiments with tetcyclacis, a cytochrome P450 monooxygenase inhibitor, indicated that inhibition of this enhanced diclofop metabolism increased diclofop-methyl phytotoxicity in this biotype. Studies with ten individual families of the resistant biotype indicated that both mechanisms of resistance, an altered target site and enhanced metabolism, are present in each individual of the population. Hence, it is likely that these two mechanisms of resistance both contribute to resistance in this biotype. © 1997 SCI.     

小麦田大穗看麦娘对精噁唑禾草灵的抗性

为明确小麦田大穗看麦娘对精噁唑禾草灵的抗性水平及产生抗性的机理,采用整株法测定了河南省小麦田大穗看麦娘种群对精噁唑禾草灵的抗性水平,以及细胞色素P450s抑制剂胡椒基丁醚(PBO)对精噁唑禾草灵的增效作用,并通过基因测序技术研究了其靶标ACCase基因的突变位点。结果显示:与敏感种群HN-06相比,抗性种群HN-05对精噁唑禾草灵的抗性倍数为52.2,其ACCase基因存在Ile-2041-Asn和Gly-2096-Ala位点突变;喷施PBO后,精噁唑禾草灵对大穗看麦娘的GR50值(有效成分)为5.4 g/hm^2,表现出明显的增效作用,与未喷施PBO处理的差异倍数为161.3。研究表明,抗性种群HN-05对精噁唑禾草灵已产生高水平抗性,该抗性的产生可能是由于其靶标基因突变和P450s介导的代谢增强同时导致的,即表现出了靶标抗性和非靶标抗性共存的现象。     

PCR-based detection of resistance to acetyl-CoA carboxylase-inhibiting herbicides in black-grass (Alopecurus myosuroides Huds) and ryegrass (Lolium rigidum gaud)

A simple method based upon allele-specific PCR was developed to detect an isoleucine-leucine substitution in the gene encoding chloroplastic acetyl-coenzyme A carboxylase (ACCase) in two gramineous weeds: Lolium rigidum Gaud and Alopecurus myosuroides Huds. Analysis of 1800 A myosuroides and 750 L rigidum seedlings showed that the presence of ACCase leucine allele(s) conferred cross-resistance to the cyclohexanedione herbicide cycloxydim and to the aryloxyphenoxypropionate herbicides fenoxaprop-P-ethyl and diclofop-methyl. Seedlings containing ACCase leucine allele(s) could be either sensitive or resistant to the aryloxyphenoxypropionate herbicides haloxyfop-P-methyl and clodinafop-propargyl. Successful detection of resistant plants in a field population of A myosuroides was achieved using this PCR assay. Using it with basic molecular biology laboratory equipment, the presence of resistant leucine ACCase allele(s) can be detected within one working day.     

Multiple herbicide‐resistant Lolium rigidum (annual ryegrass) now dominates across the Western Australian grain belt

Lolium rigidum (annual or rigid ryegrass) is a widespread annual weed in cropping systems of southern Australia, and herbicide resistance in L. rigidum is a common problem in this region. In 2010, a random survey was conducted across the grain belt of Western Australia to determine the frequency of herbicide‐resistant L. rigidum populations and to compare this with the results of previous surveys in 1998 and 2003. During the survey, 466 cropping fields were visited, with a total of 362 L. rigidum populations collected. Screening of these populations with the herbicides commonly used for control of L. rigidum revealed that resistance to the ACCase‐ and ALS‐inhibiting herbicides was common, with 96% of populations having plants resistant to the ACCase herbicide diclofop‐methyl and 98% having plants resistant to the ALS herbicide sulfometuron. Resistance to another ACCase herbicide, clethodim, is increasing, with 65% of populations now containing resistant plants. Resistance to other herbicide modes of action was significantly lower, with 27% of populations containing plants with resistance to the pre‐emergent herbicide trifluralin, and glyphosate, atrazine and paraquat providing good control of most of the populations screened in this survey. Ninety five per cent of L. rigidum populations contained plants with resistance to at least two herbicide modes of action. These results demonstrate that resistance levels have increased dramatically for the ACCase‐ and ALS‐inhibiting herbicides since the last survey in 2003 (>95% vs. 70–90%); therefore, the use of a wide range of integrated weed management options are required to sustain these cropping systems in the future.     

Mechanisms of resistance to acetyl‐coenzyme A carboxylase‐inhibiting herbicides in a Hordeum leporinum population

A failure of acetyl‐coenzyme A carboxylase (ACCase)‐inhibiting herbicides to control a population of Hordeum leporinum Link (barleygrass) occurred following eight applications of these herbicides in both crops and pastures. This population was 7.6‐fold resistant to fluazifop‐P‐butyl compared with standard susceptible populations. The population was between 3.6‐ and 3.8‐fold resistant to other ACCase‐inhibiting herbicides, except butroxydim to which it was susceptible. ACCase extracted from resistant plants and assayed in the presence of herbicides in vitro was susceptible to fluazifop acid and other aryloxyphenoxypropanoate herbicides, but was 4‐fold less sensitive to sethoxydim compared with ACCase from susceptible plants. Resistant plants metabolised fluazifop acid about 1.3‐fold more rapidly compared with susceptible plants; however, sethoxydim was metabolised equally in both populations. Resistance to fluazifop‐P‐butyl and other aryloxyphenoxypropanoate herbicides may be the result of increased herbicide detoxification, whereas resistance to sethoxydim appears to be due to a modified target enzyme. Herbicide resistance in this population is unusual in that different mechanisms appear to confer resistance to the aryloxyphenoxypropanoate and cyclohexanedione herbicides. © 2000 Society of Chemical Industry     

Cross‐resistance patterns to acetyl coenzyme A carboxylase (ACCase) inhibitors associated with different ACCase mutations in Beckmannia syzigachne

Beckmannia syzigachne (American sloughgrass) is a competitive grass weed found in China. Fenoxaprop‐P‐ethyl is widely used for control of this species in China. Resistance to fenoxaprop‐P‐ethyl in B. syzigachne has been reported to be conferred by an isoleucine(Ile)‐1781‐leucine(Leu) substitution in the gene encoding the herbicide target, acetyl‐CoA carboxylase (ACCase). In this study, three mutations were detected by derived cleaved amplified polymorphic sequence (dCAPS) method in fenoxaprop‐P‐ethyl‐resistant B. syzigachne populations: Ile‐1781‐Leu in population JCWL‐R, Ile‐2041‐Asn in JCJT‐R and Gly‐2096‐Ala in JYJD‐R. The data indicated they were genetically homogeneous (homozygous mutant) at the ACCase locus. The use of cytochrome P450 inhibitors was shown to slightly reduce the GR₅₀ value of fenoxaprop‐P‐ethyl‐resistant populations, from which we inferred a combination of target‐site resistance (TSR) and non‐target‐site resistance (NTSR) was involved in fenoxaprop‐P‐ethyl‐resistance. We characterised the cross‐resistance patterns to ACCase inhibitors in B. syzigachne. The plants in the JCWL‐R population were highly resistant to all tested APPs (aryloxyphen‐oxypropionates), sethoxydim and pinoxaden, and moderately resistant to clethodim. The plants in the JCJT‐R population were highly resistant to fluazifop‐P‐butyl, clodinafop‐propargyl, cyhalofop‐butyl, metamifop and pinoxaden; moderately resistant to haloxyfop‐R‐methyl, quizalofop‐P‐ethyl and sethoxydim; and sensitive to clethodim. The plants in the JYJD‐R population were highly resistant to clodinafop‐propargyl, metamifop and pinoxaden; moderately resistant to haloxyfop‐R‐methyl, cyhalofop‐butyl, quizalofop‐P‐ethyl, fluazifop‐P‐butyl and sethoxydim; and sensitive to clethodim. If resistance to ACCase inhibitors is present in B. syzigachne populations in the field, then our results indicate that clethodim should be used. While we demonstrated the cross‐resistance patterns of TSR resulting from three mutations in B. syzigachne, we also demonstrated that NTSR plays a role in resistance, which will complicate weed management.     

浙江稻区千金子对氰氟草酯和噁唑酰草胺的抗药性及其分子机制研究

千金子是中国直播稻田的优势禾本科杂草之一,严重威胁水稻的产量和品质。为了进一步明确浙江地区水稻田千金子对芳氧苯氧丙酸类除草剂的抗性发生情况,本研究从浙江部分稻区共采集了11个千金子种群 (其中1个为敏感种群),通过整株植物测定法检测了各种群对氰氟草酯和噁唑酰草胺的敏感性。结果显示:共有8个种群对氰氟草酯产生了抗性 (抗性指数为2.1~79.1),9个种群对噁唑酰草胺产生了抗性 (抗性指数为2.0~31.0),其中对氰氟草酯的抗性问题更为显著。在此基础上,通过基因扩增和克隆,对敏感种群和抗性种群的乙酰辅酶A羧化酶 (Acetyl-CoA carboxylase,ACCase) 基因部分序列进行比对,结果在3个抗性种群中发现突变,其中1个种群为Ile-1781-Val突变,另外2个种群则为Trp-2027-Cys突变。该研究结果表明,目前浙江部分稻区千金子种群已对氰氟草酯和噁唑酰草胺产生了抗药性,其中靶标酶基因突变是导致部分种群产生抗药性的原因之一。     

小麦田看麦娘对甲基二磺隆的抗性水平及分子机制初探

看麦娘是中国长江中下游地区稻茬麦田的主要恶性杂草之一,甲基二磺隆是防治小麦田看麦娘等禾本科杂草的重要除草剂.该研究团队前期在安徽省凤台县小麦田采集到疑似抗性种群看麦娘(AHFT-01),为明确其对甲基二磺隆的抗性发生情况及潜在的抗性机制,采用温室盆栽法在整株水平上测定了该种群对甲基二磺隆及其他乙酰乳酸合成酶(ALS)抑...     

广东省稻菜轮作区中牛筋草对十种除草剂的抗性水平及靶基因序列分析

为明确广东省稻菜轮作区中牛筋草对10种常用除草剂的抗性水平及抗性分子机制,采用整株生物测定法测定广东省稻菜轮作区内8个牛筋草种群P1～P8对草甘膦、草铵膦和乙酰辅酶A羧化酶(acetyl-CoA carboxylase,ACCase)抑制剂类等10种除草剂的抗性水平,并进一步分析P1和P8种群相关靶标酶基因5-烯醇丙酮酰莽草酸-3-磷酸合酶(5-enolpyruvyl-shikimate-3-phosphate synthase,EPSPS)、谷氨酰胺合成酶(glutamine synthetase,GS)和ACCase的部分功能区序列特征。结果显示,牛筋草P1～P8种群对草甘膦抗性指数为敏感种群的5.9倍～17.7倍,其中P8种群对草甘膦的抗性水平最高;8个种群对草铵膦也产生了不同程度的抗性,抗性指数为敏感种群的2.3倍～14.2倍,其中P1种群抗性最高。牛筋草P1和P8种群均对ACCase抑制剂类除草剂精喹禾灵、氰氟草酯和噁唑酰草胺产生了交互抗性;P1种群ACCase基因在第2 041位氨基酸处发生突变,该突变在牛筋草种群中首次发现;而P8种群ACCase基因则在第2 027位氨基...     

The role of altered acetyl-CoA carboxylase in conferring resistance to fenoxaprop-P-ethyl in Chinese sprangletop (Leptochloa chinensis (L.) Nees)

From paddy field observations in 2002 and 2004, fenoxaprop-P-ethyl resistance in Chinese sprangletop (Leptochloa chinensis (L.) Nees) has been studied using information collected from 11 sites in the Saphan-Sung district of Bangkok, Thailand. The resistant Chinese sprangletop was found in nine rice fields, whereas the susceptible Chinese sprangletop was found in only two rice fields. In greenhouse experiments, both fenoxaprop-P-ethyl-resistant and susceptible Chinese sprangletop from the same location were investigated for 50% growth reduction based on phytotoxicity, plant height and fresh and dry weight. The resistant Chinese sprangletop showed apparent resistance at 14-21 days after herbicide application at a rate of 21.1-337.6 g AI ha(-1). The resistance index of resistant Chinese sprangletop was 10-25 times higher than that of the susceptible Chinese sprangletop. In addition, Chinese sprangletop did not exhibit multiple resistance to oxadiazon, propanil and quinclorac. According to acetyl-CoA carboxylase (ACCase) assays, the level of ACCase specific activity in the resistant Chinese sprangletop was significantly higher than that in the susceptible Chinese sprangletop. Similarly, the ACCase activity of the resistant Chinese sprangletop was 10 times less sensitive to fenoxaprop-P-ethyl than that of the susceptible Chinese sprangletop, based on the I50 values. The present study of the mechanism responsible for resistance in the biotypes investigated indicated that there was a close association between the concentration-response at the whole-plant level and ACCase sensitivity to fenoxaprop-P-ethyl, and resistance to fenoxaprop-P-ethyl was conferred by a modified ACCase at the target site, as suggested by higher specific activity and less sensitivity to the herbicide.     

上海市水稻田千金子对3种乙酰辅酶A羧化酶抑制剂的抗性现状及酶突变机制

为明确上海市水稻田千金子对乙酰辅酶A羧化酶 (ACCase) 抑制剂类除草剂的抗性发生情况及可能存在的抗性机制,在上海市千金子发生严重地区的水稻田共采集51个种群,采用单剂量抗性甄别法测定了不同千金子种群对3种ACCase抑制剂类除草剂的抗性水平,扩增和比对了靶标酶ACCase基因部分片段的差异。结果显示:在氰氟草酯105 g/hm2有效成分剂量选择压下,8个千金子种群标记为抗性种群,6个种群为发展中抗性种群;在噁唑酰草胺 120 g/hm2有效成分剂量选择压下,4个千金子种群标记为抗性种群,5个种群为发展中抗性种群;在精噁唑禾草灵62.1 g/hm2有效成分剂量选择压下,6个千金子种群标记为抗性种群,2个种群为发展中抗性种群。对15个抗性千金子种群靶标酶基因片段的测序发现,9个种群共发生了4种ACCase基因突变类型,分别为ACCase基因 1999 位点色氨酸 (TGG) 突变为丝氨酸 (TCG)、1999位点色氨酸 (TGG) 突变为半胱氨酸 (TGT)、2027位点色氨酸 (TGG) 突变为丝氨酸 (TCG) 以及2027位点色氨酸 (TGG) 突变为半胱氨酸 (TGT/TGC)。其中,5个抗性千金子种群ACCase 基因突变频率均大于60%。研究表明,ACCase抑制剂类除草剂抗性千金子在上海市部分地区发生已较为严重,ACCase 基因突变是导致不同千金子种群对该类除草剂产生抗性的重要原因之一。     

安徽省稻田千金子对氰氟草酯和噁唑酰草胺的抗性及其靶标分子机制

为明确安徽省稻田杂草千金子Leptochloa chinensis对氰氟草酯和噁唑酰草胺的抗性，从安徽省12个市38个县（市、区）稻区千金子发生较严重的田块中共采集72个千金子种群，采用整株生物测定法检测其对氰氟草酯和噁唑酰草胺的抗性，筛选同时对噁唑酰草胺和氰氟草酯有疑似抗性的千金子种群并测定其对这2种药剂的抗性水平，同时利用分子生物学技术检测千金子高抗种群的乙酰辅酶A羧化酶（acetyl-CoA carboxylase,ACCase）基因是否发生抗性位点氨基酸突变。结果显示，在72个千金子种群中，13个千金子种群已对氰氟草酯产生抗性，5个千金子种群已对噁唑酰草胺产生抗性；AH-1、AH-3、AH-7、AH-34和AH-72这5个千金子种群同时高抗氰氟草酯和噁唑酰草胺，其中对氰氟草酯的抗性指数介于21.98～65.52之间，对噁唑酰草胺的抗性指数介于11.76～27.19之间；这5个种群的ACCase基因片段均在2 027位点发生氨基酸突变，色氨酸突变为半胱氨酸；此外AH-3和AH-72这2个种群在1 999位点也由色氨酸突变为半胱氨酸，表明安徽省千金子已经对氰氟草酯和噁唑酰草胺产生交...