微生物及其天然产物防治杂草的发展及展望

概述了利用微生物及其天然产物防治杂草的潜在优势和研究进展，介绍已商品化和具有开发潜力的微生物除草剂及具有除草活性的微生物天然植物毒素。     

真菌除草剂——杂草生物防治的进展

一般说来,比较理想的除草剂应该符合生产简便、容易贮藏、廉价高效以及对人和环境安全等要求。显然,某些侵染杂草的病原真菌具备其中的大多势特点。在过去10年中,已就利用植物病原真菌进行生物除草的问题进行了广泛研究。其使用方法主要有经典式和淹没式(inundati-     

葱紫斑病菌毒素的纯化及除草活性

随着人们对植物病原真菌毒素研究和认识的深入,毒素在农药研究中的应用也日趋广泛,特别是把植物病原真菌毒素作为开发除草剂的内源活性物质已有成功的实例。Suemitsu等报道葱紫斑病菌(Alternaria porri)毒素(以下简称AP-毒素)由4种物质组成,但有关其除草生物活性研究目前尚未见报道。作者对AP-毒素的分离提纯及对稗草的生物活性作了初步研究,结果如下。 1 材料与方法 1.1 供试材料:菌种:葱紫斑病菌(Alternaria porri)是由典型病斑分离获得的纯培养物。     

湖北省水稻田稗草病原真菌资源调查

为了解湖北省水稻田恶性杂草稗草上的病原真菌种类,以期为更好地利用植物病原真菌资源和开发生物除草剂奠定基础。采用组织分离法对稗草病害样品进行分离,结合形态观察和rDNA ITS序列分析对菌株进行鉴定,最后用人工接种法对部分菌株进行致病性测定。从53份自然发病的稗草样品中分离到86个菌株,共鉴定出7个属的13种真菌。     

生物源除草活性物质开发及应用研究进展

生物源除草剂是一种环境友好型除草剂,是未来除草剂的发展方向之一。本文从生物源除草剂应用的角度出发,综述了历年来国内外生物源除草活性物质在除草领域的研究进展,对生物源除草活性物质及其衍生物的开发和应用现状进行了系统的归纳和总结。其中植物源除草活性物质包括松科、桃金娘科、芸香科、唇形科和菊科等植物的提取物、分泌物和化学改性衍生物;微生物源除草活性物质包括真菌、细菌、放线菌、病毒和它们的次生代谢产物。本文可为生物源除草剂的开发和应用提供一定参考。     

化学除草的选择性原理

选择性除草剂是一类能杀死杂草或严重抑制杂草生长而又不大伤害庄稼的农药。除草剂仅在一定的范围内对某些作物具有选择性,其选择的范围取决于多种因素。由于在任何地区都存在着植物、环境和除草剂之间复杂的相互关系,这些关系变化无常,环境条件与施药方法不同,除草剂的灭草效果亦不一样。了解化学除草的选择性,有助于提高除草的效果。植物的作用植物(包括杂草和作物)对除草剂的反应受其遗传、叶龄、生长速度、形态和生理以及生物物理和生物化学过程等因素的影响,不同属(genus)的植物反应是不同的,而同属植     

农田杂草抗药性研究方法简介

近20年来,抗除草剂的杂草生物型迅速增加,而且蔓延很快,目前已经明确获得抗药性的杂草生物型已近100种,对某些国家和地区的农业生产已构成威胁。我国发展农田化学除草已有30多年历史,近年来在一些长期使用单一除草剂的农田,由于多次用药或     

新型稻田除草剂去稗安的应用技术

去稗安是由日本安万特作物科学公司生产的稻田除草剂 ,在日本主要是在移栽稻田上应用 ,药效期长 ,除草活性高 ,对千金子、稗草特效 ,对莎草及阔叶杂草高效 ,对水稻及环境有较高安全性 ,扩散性好 ,可直接用瓶甩施 ,除草作业省力。1　去稗安的特点1 1　作用机理去稗安是新型的杂环类除草剂 ,具有内吸传导性。通用名oxaziclomefone ,剂型为 1%悬浮剂 ,主要由杂草的根和茎叶基部吸收 ,除草机理是阻碍植物内生GA3 激素的形成 ,使杂草茎叶失绿 ,生长受抑制 ,直至枯死。杀草保苗的原理主要是药剂在水稻与杂草中的吸收传导以及代谢速度的差异所致。…     

生防菌株BL-21的鉴定及其活性产物

为了明确生防菌株BL-21的分类地位和发酵液中的有效成分,对其进行了鉴定,并对其发酵液的抑菌谱和稳定性进行了测定。结果表明,该菌株为侧孢芽孢杆菌Bacillus laterosporus;其发酵液对全部供试植物病原真菌均有抗菌活性;发酵液中的抗菌活性物质对热和蛋白酶敏感,100℃10min、酶解37℃120min活性丧失;从菌株BL-21的发酵液中分离得到四种抗菌物质,均具有抗革兰氏阳性菌的活性,其中A组分和B组分还对植物病原真菌有抑制作用。     

植物源羊脂酸除草活性及其响应机制

为研制新型植物源除草剂,需从植物中筛选具有除草活性的天然产物,本研究将椰子经物理压榨成椰子油,椰子油经皂化、酸化、蒸馏分段,再经气质联用仪鉴定其中具有除草活性的产物,并采用室内生测法和田间药效试验对该产物的除草活性进行评价,测定其在不同光照和浓度条件下对小飞蓬Conyza canadensis的3种防御酶——L-苯丙氨酸解氨酶、多酚氧化酶和过氧化物酶活性的影响。结果表明:从椰子油中筛选的具有除草活性的产物经鉴定为羊脂酸,气质色谱图中保留时间为6.20 min。羊脂酸具有较高的除草活性,EC_(50)为14.07 mg/L,100 m L的20%羊脂酸水乳剂喷施后15 d对20 m~2非耕地杂草的株防效和鲜重防效分别为90.25%和90.37%,即与对照药剂草甘膦异丙胺盐水剂除草效果相当。低浓度羊脂酸对小飞蓬的防御酶活性影响不显著,较高浓度下L-苯丙氨酸解氨酶活性显著上升,多酚氧化酶和过氧化物酶活性显著下降,当光强为100~120μmol·m~(-2)·s~(-1)、温度为18~20℃时,这种变化在完全黑暗条件下较完全光照条件下更为明显。表明羊脂酸除草机理可能与其抑制杂草的光合作用有关。     

Natural products as sources of herbicides: current status and future trends

Although natural product-based discovery strategies have not been as successful for herbicides as for other pesticides or pharmaceuticals, there have been some notable successes. Phosphinothricin, the biosynthetic version of glufosinate, and bialaphos are phytotoxic microbial products that have yielded commercial herbicides. Cinmethylin, a herbicidal analogue of cineole, has been sold in Europe and Asia. The triketone herbicides are derivatives of the plant-produced phytotoxin leptospermone. These products represent only a small fraction of commercialized herbicides, but they have each introduced a novel molecular target site for herbicides. Analysis of the literature reveals that phytotoxic natural products act on a large number of unexploited herbicide target sites. The pesticide industry's natural product discovery efforts have so far concentrated on microbially derived phytotoxins, primarily from non-pathogenic soil microbes, involving the screening of large numbers of exotic isolates. Plant pathogens usually produce potent phytotoxins, yet they have received relatively little attention. Even less effort has been made to discover plant-derived phytotoxins. Bioassay-directed isolation has been the preferred method of discovery after a producing organism is selected. This laborious approach often leads to rediscovery of known compounds. Modern tandem separation/chemical characterization instrumentation can eliminate much of this problem by identification of compounds before they are bioassayed.     

Rationale for a natural products approach to herbicide discovery

Weeds continue to evolve resistance to all the known modes of herbicidal action, but no herbicide with a new target site has been commercialized in nearly 20 years. The so-called 'new chemistries' are simply molecules belonging to new chemical classes that have the same mechanisms of action as older herbicides (e.g. the protoporphyrinogen-oxidase-inhibiting pyrimidinedione saflufenacil or the very-long-chain fatty acid elongase targeting sulfonylisoxazoline herbicide pyroxasulfone). Therefore, the number of tools to manage weeds, and in particular those that can control herbicide-resistant weeds, is diminishing rapidly. There is an imminent need for truly innovative classes of herbicides that explore chemical spaces and interact with target sites not previously exploited by older active ingredients. This review proposes a rationale for a natural-products-centered approach to herbicide discovery that capitalizes on the structural diversity and ingenuity afforded by these biologically active compounds. The natural process of extended-throughput screening (high number of compounds tested on many potential target sites over long periods of times) that has shaped the evolution of natural products tends to generate molecules tailored to interact with specific target sites. As this review shows, there is generally little overlap between the mode of action of natural and synthetic phytotoxins, and more emphasis should be placed on applying methods that have proved beneficial to the pharmaceutical industry to solve problems in the agrochemical industry.     

Pathogens and their products affecting weedy plants

There are many natural enemies of weedy plants; among them are plant pathogens. Plant pathogens are capable of affecting plants, in part because of the phytotoxins they produce. Phytoloxins of weedy pathogens are produced in culture media by most of the phytopathogenic fungi of weeds that we have studied. In most cases the phytotoxin(s) usually belongs to a family of related compounds produced by the pathogen. Phytotoxin production in the medium can be optimized by placement of the host extract into the medium. Lethal activity is usually observed in the concentration range of 10^-3-10^-6M. The concept of using these molecules, or derivatives thereof, or related compounds as herbicides, should be explored.     

Phytotoxic sites of action for molecular design of modern herbicides (Part 1): The photosynthetic electron transport system

A bird's eye review was tried to select the bio‐rational targets from known and novel plant‐specific ones for the molecular design of modern herbicides, which exhibit efficient phytotoxicity at a low‐use rate and preserve a good environment in the 21st century. In phytotoxic sites in the photosynthetic electron transport (PET) system discussed in the present article (Part 1), the generally called bleaching herbicides interfering with the biosynthesis of photosynthetic pigments, chlorophylls and carotenoids, and the biosynthesis of plastoquinone, were considered to be good models for the molecular design of modern herbicides. The PET itself was still considered as an interesting target site for new herbicides, although they need to exert their action in all green leaves of weeds to achieve herbicidal efficacy. Because these herbicides never form a tight binding with D1‐protein, their use‐rate cannot be expected to be as low as the herbicides inhibiting chlorophyll or branched amino‐acid biosynthesis. Other herbicidal targets found in chloroplasts, namely ATP and NADPH formations, have already been omitted from the worldwide biorational molecular design program of herbicides targeting the PET system.     

Chlorophyll fluorescence as a marker for herbicide mechanisms of action

Photosynthesis is the single most important source of O₂ and organic chemical energy necessary to support all non-autotrophic life forms. Plants compartmentalize this elaborate biochemical process within chloroplasts in order to safely harness the power of solar energy and convert it into usable chemical units. Stresses (biotic or abiotic) that challenge the integrity of the plant cell are likely to affect photosynthesis and alter chlorophyll fluorescence. A simple three-step assay was developed to test selected herbicides representative of the known herbicide mechanisms of action and a number of natural phytotoxins to determine their effect on photosynthesis as measured by chlorophyll fluorescence. The most active compounds were those interacting directly with photosynthesis (inhibitors of photosystem I and II), those inhibiting carotenoid synthesis, and those with mechanisms of action generating reactive oxygen species and lipid peroxidation (uncouplers and inhibitors of protoporphyrinogen oxidase). Other active compounds targeted lipids (very-long-chain fatty acid synthase and removal of cuticular waxes). Therefore, induced chlorophyll fluorescence is a good biomarker to help identify certain herbicide modes of action and their dependence on light for bioactivity.     

HPPD抑制剂的机理与应用进展

HPPD是在植物光合作用过程中发现的一类新型除草剂靶标酶,可以催化对羟苯基丙酮酸氧化脱羧转变为尿黑酸。HPPD抑制剂的抑制作用会导致植物分生组织产生白化症状,最终死亡。本文对HPPD的作用机理以及HPPD抑制剂主要品种的应用作了综述。     

Phytotoxicants from microorganisms and related compounds

Phytotoxic compounds produced by microorganisms are reviewed. Their utilisation as leads to new herbicides is explored in three chemical classes : 2-aminoalk-3-enoic acids, ether derivatives of 3-hydroxycyclobut-3-ene-1,2-diones, and 2-(acylaminooxy)acetic acid derivatives. It is concluded that some bacteria and fungi yield compounds possessing sufficient herbicidal activity to be valuable as herbicides as such, or as leads for chemical optimisation.     

Mechanisms of action and structure activity relations of herbicides that inhibit photosynthesis

A survey and chemical classification are given for the most important herbicidal inhibitors of photosynthesis. The photochemical reactions involved in photosynthesis are reviewed. The herbicides discussed here all interfere with photosynthetic electron transport in the light reactions. Comments are made on the redox catalysts and the electron transport chain. The mode of action of the herbicides due to inhibition of the light reactions I and II or of photophosphorylation are described. Structure activity correlations according to the regression analysis (Hansch-approach) are discussed with examples in the classes of acetanilides, benzimidazoles and triazinones. The correlation studies in the series of the Hill-reaction inhibitors have led to a model for the essential structural elements. Some work on the problem of selectivity and its importance is reviewed.     

Synthesis and herbicidal potential of substituted aurones

BACKGROUND: With the objective of exploring the herbicidal activity of substituted aurones, a series of 4,6‐disubstituted and 4,5,6‐trisubstituted aurones were synthesised, and their herbicidal activities against Brassica campestris L. and Echinochloa crusgalli (L.) Beauv. were evaluated in laboratory bioassays. Effects of some of the compounds were evaluated on seed germination. The most active compounds in the laboratory were evaluated in the greenhouse. RESULTS: The compounds were characterised by ¹H NMR, ¹³C NMR and HRMS; some of them were further identified by IR. A (Z)‐configuration was assigned to the aurones, based on spectroscopic and crystallographic data. Bioassay results of root growth showed that the aurones had a moderate herbicidal activity against the dicotyledonous plant Brassica campestris. (Z)‐2‐Phenylmethylene‐4,6‐dimethoxy‐3(2H)‐benzofuranone(6o) was the most active compound, with 81.3 and 88.5% inhibition at 10 and 100 µg ml^?1 respectively, equal to the activity of mesotrione. Some of the aurones possessed some inhibition of germination on several plant species. For glasshouse tests, the substituted aurones had lower herbicidal activity than metolachlor and mesotrione. CONCLUSION: It is possible that aurone derivatives, which possess structures different from those of the commercial herbicides, may become novel lead compounds for the development of herbicides against dicotyledonous weeds with further structure modification. Copyright © 2012 Society of Chemical Industry