抑制ALS的除草剂新品种及在我国的应用前景

作用靶标为乙酰乳酸合成酶（ＡＬＳ）的除草剂近年有了长足的发展，由最初的磺酰脲类，咪唑啉酮类除草剂发展至今的三唑并嘧啶磺酰苯胺类，嘧啶氧代苯甲酸类等品种，这些新品种具有活性高，用药量极低，对哺乳动物低毒，对环境影响较小等优异的特点，近年开发的一些新品种正代表着未来除草剂的发展方向，本文介绍了近年世界各大公司新开发的ＡＬＳ抑制剂，并就其在中国的应用前景进行了讨论。     

甜菜田除草剂应用研发进展

本文介绍了甜菜田经常使用的19个除草剂,包括芳氧苯氧羧酸类6个、环己二酮类2个、酰胺类3个、(硫代)氨基甲酸酯类4个、二硝基苯胺类2个、三嗪类1个、苯并呋喃甲磺酸酯类1个。提出了可以在甜菜田筛选的9个除草剂,包括磺酰脲类5个、磺酰胺类4个。简述了甜菜田除草剂的选用策略。     

三唑并嘧啶磺酰胺类除草剂的研究概况

三唑并嘧啶磺酰胺类除草剂是将磺酰脲类除草剂通过脲桥的结构改造和修饰而得,它既保持了磺酰脲类除草剂的超高效性,又克服了一些磺酰脲类除草剂品种在土壤中残留期较长、易对后茬作物造成伤害等缺点。本文综述了三唑并嘧啶磺酰胺类除草剂的结构、主要品种、作用机理、应用研究和发展前景。     

磺酰脲类除草剂的使用与杂草抗药性

1970年首次报道了杂草对均三氮苯类除草剂产生抗性,杂草对除草剂的抗性也随着除草剂的使用而不断发展与蔓延。到目前为止,已有100种以上杂草对不同类型除草剂产生了抗性,其中涉及均三氮苯、联吡啶、苯氧羧酸、苯基脲、二硝基苯胺、芳氧苯氧丙酸、环己烯酮、三唑、咪唑啉酮、磺酰脲等,从而使杂草抗性成为除草剂品种开发及化学除草中的重要问题。在杂草对众多类型除草剂产生抗性的事例中,杂草对超高效除草剂磺酰脲类化合物的抗性最引人注目。     

乙酰辅酶A羧化酶抑制剂类除草剂与杂草的抗药性

乙酰辅酶A羧化酶(ACCase)是芳氧苯氧基丙酸类(AOPP)除草剂和环己烯酮类(CHD)除草剂的作用靶标酶，这类除草剂对禾本科杂草有优异的防除效果，属于超高效型除草剂，使用范围较广，但同时也发现连续使用该类除草剂，杂草容易产生抗药性。本文概述了AOPP和CHD类除草剂的现状、作用机理及抗该类除草剂杂草的分布、危害，并探讨了杂草对该类除草剂的抗性机理、抗性控制等。     

除草剂的药害(续)

三、药害的原因除草剂发生药害的根本原因是由于使用不当,发生逆向选择的结果。此外还有农药生产和管理上的原因等。 (一) 内在原因——除草剂的逆向选择作用 1.形态的逆向选择:2,4—D等苯氧羧酸类除草剂或苯甲酸类的百草敌等具有激素作用的除草剂用于阔叶作物,由于双子叶植物生长点裸露接受药剂以及生理生化的逆向选择而产生药害。由叶片吸收的除草剂采用表面活性剂并且大水量喷洒,药液在阔叶作物的叶缘聚积,结果发生药害。所以由叶片吸入的除草剂加了表面活性剂之后,可能因削弱选择作用而容易发生药害。     

靶酶与除草剂品种的设计与开发

80年代以来,随着国际市场上油价下跌,适用作物、防治对象及使用方法相同或基本一致的同类及不同类型除草剂品种增多,播种面积缩小,增效剂普遍应用,复配制剂增多,导致除草剂品种竞争日趋激烈;在此形势下,各农药公司为保持更强的竞争力,大力投资开发高活性新品种,在二苯醚类、芳氧苯氧基丙酸类、磺酰脲类、咪唑啉酮类、环己烯二酮类等取得了突破性进展,开发出一系列高效与超高效新品种。     

乙酰辅酶A羧化酶抑制剂的研究进展

乙酰辅酶A羧化酶(ACCase)是除草剂的作用靶标之一，此类除草剂主要有两类：芳氧苯氧丙酸类(APP)和环己烯酮类(环己二酮，环己烯二酮，CHD)。本文就ACCase抑制剂的发展历史、合成方法、结构与活性和除草机制等方面作了概述。     

杂草对芳氧苯氧丙酸类(APPs)除草剂的抗性分子机理研究进展

芳氧苯氧丙酸类（aryloxyphenoxypropionates,APPs）除草剂是一类广泛使用的乙酰辅酶A羧化酶抑制剂,可高效专一抑制禾本科杂草的乙酰辅酶A羧化酶（acetyl-coenzyme A carboxylase,ACCase）。目前已出现大量抗芳氧苯氧丙酸类除草剂的禾本科杂草,其抗性大多由叶绿体乙酰辅酶A羧化酶的羧基转移酶（carboxyltransferase,CT）功能域中的氨基酸突变引起。在所有已发现的氨基酸突变中,最引人关注的是第1 781位（对应大穗看麦娘Alopecurus myosuroides质体ACCase的氨基酸残基位置）异亮氨酸到亮氨酸的单点突变,该特定位置形成亮氨酸会导致某些杂草对APPs类除草剂产生抗性。综述了乙酰辅酶A羧化酶CT功能域的研究进展及杂草对APPs类除草剂的抗性分子机理,探讨了杂草对APPs类除草剂抗性分子机理研究中存在的问题,以期为进一步深入研究APPs类除草剂的抗性机制提供参考。     

农得时防除稻田杂草应用技术

在防除稗草的稻田,莎草和阔叶杂草上升为主要害草,且以往的除草剂不能很好地清除多年生杂草,为此,自1985年开始用美国杜邦公司研制的苗后处理剂农得时(Lo-nax)〔化学名称为2-(4,6-二甲氧基嘧啶-2-基氨基羰基硫酰甲基)苯甲酸甲酯〕进行了水稻直播和移栽本田的应用技术研究。     

除草剂剂型的研究与发展

除草剂的普遍应用带动了剂型的迅速发展,同时许多新剂型和先进技术的应用,也使除草剂的发展有了更广阔的空间。本文对除草剂剂型进行了总体介绍,概述了其研究现状及改良方向,展望了未来除草剂剂型的研发趋势。     

Computational analysis of mutated AHAS in response to sulfonylurea herbicides

Sulfonylurea (SU) herbicides that target acetohydroxyacid synthase (AHAS, also called acetolactate synthase (ALS)) are regarded as one of the most important classes of herbicides, due to their extremely low toxicity towards mammals, ultra‐low dosage application and high selectivity. However, mutations of AHAS to a herbicide‐insensitive form appear to be a worldwide problem for acquired resistance. In this study, three mutated AHAS sequences were used. In the mutated AHASs, the proline (Pro) was replaced by one of threonine (Thr), alanine (Ala) or serine (Ser) in AHAS amino acid (AA) position 197Pro. To understand the herbicide resistance mechanism, we built dimeric AHAS complex models based on 1YBH of protein data bank (PDB) with SU herbicide, chlorimuron ethyl (CIE), using a homology. The three mutated AHASs in complex with CIE were analysed, and the resistance mechanism to SU herbicides was studied by molecular dynamics (MD) simulation performed using GROMACS 4.5.5. MD simulation analysis of wild‐type and the three mutated dimeric AHAS–CIE complex systems revealed the conformational stability and changes in herbicide binding to dimeric AHAS system due to the mutation. Additionally, it showed that conformational change of amino acid residue 200Met (methionine) was associated with the imidazolinone herbicide resistance mechanism. According to our computation, the detailed mechanism of herbicide resistance was variable, depending on the type of mutated amino acid, providing new insights for designing herbicides specific to each mutant AHAS.     

近年我国农田杂草防控中的突出问题与治理对策

我国田园杂草有1 400多种,严重危害的130余种,恶性杂草37种。我国杂草发生面积约9 246.7万hm2次,防治面积1.04亿hm2次,挽回粮食损失2 699万t,每年主粮作物仍有近300万t产量损失。杂草防控中的突出问题是:杂草群落演替,难治杂草种群增加;除草剂单一使用,杂草抗药性发展迅速;除草剂对作物药害频发,影响种植结构调整;新除草剂创制能力不足,难以满足不同作物田除草需求;农村劳动力短缺,杂草防控更依赖于化学防治。解决上述问题,应实施以下对策:加强杂草发生危害的监测预警,科学轮换使用除草剂,推广除草剂减量与替代技术,加快新除草剂研制及推广应用,加速耐除草剂作物商业化进程,推进统防统治及农民培训。     

Historical review of rice herbicides in Japan

A historical review on rice herbicides in Japan was conducted. Rice cropping patterns (transplantation and flooded or dry‐direct seedings) are described, followed by a comparison of the economics of hand weeding and herbicide use. Changes of herbicide chemicals, formulations and application methods are also described. Weeds resistant even to herbicides designed for use with rice agriculture were found. Mode of action and selectivity mechanism of these herbicides are discussed from the standpoint of fish toxicity, which is especially important in rice culture. Finally, a view for the future is presented.     

Recent developments in auxin biology and new opportunities for auxinic herbicide research

Auxinic herbicides mimic the effects of natural auxin. However, in spite of decades of research, the site(s) of action of auxinic herbicides has remained unknown and many physiological aspects of their function are unclear. Recent advances in auxin biology provide new opportunities for research into the mode of action of auxinic herbicides. Of considerable interest is the discovery of auxin receptors (TIR1 and possibly ABP1) that may lead to the discovery of auxinic herbicide site(s) of action. Knowledge of auxin-conjugating enzymes and auxin signal transduction components may shed new light on herbicide activity, selectivity in dicots, and mechanisms leading to phytotoxicity in sensitive plants. Analysis of genes induced in response to auxin may provide a novel approach for detection of off-target herbicide injury in crops. For example, the auxin-responsive gene GH3 is highly and specifically induced in response to auxinic herbicides in soybean, and may offer a novel method for diagnosing auxinic herbicide injury. Advances in our understanding of auxin biology will provide many new avenues and opportunities for auxinic herbicide research in the future.     

The possible role of quinate in the mode of action of glyphosate and acetolactate synthase inhibitors

BACKGROUND: The herbicide glyphosate inhibits the biosynthesis of aromatic amino acids by blocking the shikimate pathway. Imazethapyr and chlorsulfuron are two herbicides that act by inhibiting branched‐chain amino acid biosynthesis. These herbicides stimulate secondary metabolism derived from the aromatic amino acids. The aim of this study was to test if they cause any cross‐effect in the amino acid content and if they have similar effects on the shikimate pathway. RESULTS: The herbicides inhibiting two different amino acid biosynthesis pathways showed a common pattern in general content of free amino acids. There was a general increase in total free amino acid content, with a transient decrease in the proportion of amino acids whose pathways were specifically inhibited. Afterwards, an increase in these inhibited amino acids was detected; this was probably related to proteolysis. All herbicides caused quinate accumulation. Exogenous application of quinate arrested growth, decreased net photosynthesis and stomatal conductance and was ultimately lethal, similarly to glyphosate and imazethapyr. CONCLUSIONS: Quinate accumulation was a common effect of the two different classes of herbicide. Moreover, exogenous quinate application had phytotoxic effects, showing that this plant metabolite can trigger the toxic effects of the herbicides. This ability to mimic the herbicide effects suggests a possible link between the mode of action of these herbicides and the potential role of quinate as a natural herbicide. Copyright © 2009 Society of Chemical Industry     

Prevalence of herbicide‐resistant weed species in Malaysian rice fields: A review

The management of weeds in Malaysian rice fields is very much herbicide‐based. The heavy reliance on herbicide for weed control by many rice‐growers arguably eventually has led to the development and evolution of herbicide‐resistant biotypes in Malaysian rice fields over the years. The continuous use of synthetic auxin (phenoxy group) herbicides and acetohydroxyacid synthase‐inhibiting herbicides to control rice weeds was consequential in leading to the emergence and prevalence of resistant weed biotypes. This review discusses the history and confirmed cases and incidence of herbicide‐resistant weeds in Malaysian rice fields. It also reviews the Clearfield Production System and its impact on the evolution of herbicide resistance among rice weed species and biotypes. This review also emphasizes the strategies and management options for herbicide‐resistant rice field weeds within the framework of herbicide‐based integrated weed management. These include the use of optimum tillage practices, certified clean seeds, increased crop competition through high seeding rates, crop rotation, the application of multiple modes of action of herbicides in annual rotations, tank mixtures and sequential applications to enable a broad spectrum of weed control, increase the selective control of noxious weed species in a field and help to delay the resistance evolution by reducing the selection pressure that is forced on those weed populations by a specific herbicidal mode of action.     

A novel genomic approach to herbicide and herbicide mode of action discovery

A herbicide with a new mode of action has not been commercialized for more than 30 years. A recent paper describes a novel genomic approach to herbicide and herbicide mode of action discovery. Analysis of a microbial gene cluster revealed that it encodes genes for both the biosynthetic pathway for production of the sesquiterpene aspterric acid and an aspterric acid‐resistant form of dihydroxy acid dehydratase (DHAD), its target enzyme. Aspterric acid is weak compared with commercial synthetic herbicides, and whether DHAD is a good herbicide target is unclear from this study. Nevertheless, this genomic approach provides a novel strategy for the discovery of herbicides with new modes action. © 2018 Society of Chemical Industry     

Cross-resistance pattern and alternative herbicides for Cyperus difformis resistant to sulfonylurea herbicides in Korea

A Cyperus difformis L accession from Chonnam province, Korea was tested for resistance to the sulfonylurea herbicide, imazosulfuron. The accession was confirmed to be resistant (R) and was cross-resistant to other sulfonylurea herbicides, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, the pyrimidinyl thiobenzoate herbicide, bispyribac-sodium, and the imidazolinone herbicide imazapyr, but not to imazaquin. Multiple resistance was tested using twelve herbicides with target sites other than acetolactate synthase (ALS). The R biotype could be controlled by other herbicides with different modes of action such as butachlor, carfentrazone-ethyl, clomeprop, dithiopyr, esprocarb, mefenacet, oxadiazon, pretilachlor, pyrazolate and thiobencarb, applied to soil at recommended rates. Several sulfonylurea herbicide-based mixtures can control both the R and S biotypes of C difformis, except sulfonylurea plus dimepiperate, molinate or pyriftalid, and pyrazolate plus butachlor. Although mixtures of sulfonylurea herbicides might be more effective, they should be avoided and used only in special cases. In terms of in vitro ALS activity, the R biotype was 1139-, 3583-, 1482-, 416-, 5- and 9-fold more resistant to bensulfuron-methyl, cyclosulfamuron, imazosulfuron, pyrazosulfuron-ethyl, bispyribac-sodium and imazapyr, respectively, than the S biotype. The in vivo ALS activity of the R biotype was also less affected by the sulfonylurea herbicides, imazosulfuron and pyrazosulfuron-ethyl, than the S biotype. Results of in vitro and in vivo ALS assays indicated that the resistance mechanism of C difformis to ALS inhibitor herbicides was primarily due to an alteration in the target enzyme, ALS. Greenhouse experiments showed delayed flowering and reduced seed production of the R biotype, which could possibly result in reduced fitness. This unusual observation needs to be confirmed in field situations.     

喷雾助剂对茎叶处理除草剂的增效机制及应用研究进展

农田草害的发生严重影响了农业生产和发展，使用除草剂进行化学防治是目前最省时省力和防除效果最好的除草方法。其中，茎叶处理除草剂因其具有不受土壤环境影响、按草施药、灵活和选择性高等优点，应用范围更广。然而，茎叶处理除草剂在喷雾施药过程中由于受到杂草叶片界面特性的影响，常出现药液迸溅、滚落、难以渗透等现象，导致除草剂用量增大，杂草产生抗性，并出现药害和环境残留等诸多问题。使用合适的喷雾助剂是解决以上问题的重要策略。考虑到除草剂的使用需要结合杂草性质，并与喷雾助剂一起使用，了解各自的作用方式对指导草害的防治具有重要意义。本文在介绍除草剂作用方式和应用现状的基础上，总结了禾本科、阔叶类和莎草科杂草的形态学和叶片界面特性及其对除草剂选择的影响，并详细阐述了常用喷雾助剂对茎叶处理除草剂的增效机制及其剂量传递过程的影响。在此基础上，分别归纳了喷雾助剂对触杀型和内吸传导型除草剂在防除禾本科、阔叶类、莎草科杂草方面的应用及增效规律。此外，文章还对除草剂喷雾助剂的未来发展方向进行了展望，以期为除草剂领域喷雾助剂的研发和使用提供参考，并最终实现农药的“减施增效”。