Non-streptomycete actinomycetes as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters

Among soil microorganisms, bacteria and fungi and to a lesser extent actinomycetes, have received considerable attention as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters. Within actinomycetes, Streptomyces spp. have been investigated predominantly, mainly because of their dominance on, and the ease of isolation from, dilution plates and because of the commercial interest shown on the antibiotics produced by certain Streptomyces spp. Many of non-streptomycete actinomycetes (NSA) taxa are therefore rarely reported in literature dealing with routine isolations of biocontrol agents and/or plant growth promoters from plant and soil. It is clear that special isolation methods need to be employed in routine isolations to selectively isolate NSA. Some interesting information exists, albeit in relatively few reports compared to that on other microorganisms, on the biological activities of NSA, especially in relation to their mechanisms of action in the biological control of soil-borne fungal plant pathogens and plant growth promotion. This review presents an overview of this information and seeks to encourage further investigations into what may be considered a relatively unexplored area of research. Certain soil environmental factors, especially in horticultural systems, could be manipulated to render the soil conducive for the biological activities of NSA. A variety of NSA isolated by selective methods have not only shown to be rhizosphere competent but also adapted for an endophytic life in root cortices. Some of the NSA, including endophytic strains that have shown potential to suppress soil-borne fungal plant pathogens, are able to employ one or more mechanisms of antagonism including antibiosis, hyperparasitism and the production of cell-wall degrading enzymes. Strains of NSA promote plant growth by producing plant growth regulators. Enhancement of plant growth by the antagonists are considered to help the host by producing compensatory roots that mask the impact of root diseases.     

连作障碍发生机理研究进展

随着集约化种植程度的不断提高,作物连作导致产量和品质下降,土传病害严重发生,严重制约了现代农业的可持续发展,连作障碍发生机理一直是国内外学者研究的热点之一。近年来,国内外学者从多方面、多角度对连作障碍进行了研究,但这些研究多集中于单一因素分析,缺乏对不同因子内在相互关系和本质的了解,未能深入揭示连作障碍发生的真正原因。深入认识连作障碍的成因及各要素间的互作关系是防控作物土传病原微生物生长、缓解连作障碍、实现农药使用量零增长的基础。本文从土壤理化性状及生物学性状恶化、植物生理抗性下降和连作自毒作用等方面系统综述了连作障碍发生机理,分析了连作障碍因素间的相互关系并对该领域未来的研究方向进行了展望,以期为寻找安全、环保和有效的缓解措施提供理论依据。     

Rapid methods for diagnosis of soil-borne plant pathogens

Abstract. Root diseases are often hard to identify or quantify visually, particularly by the inexperienced, so several modern methods of diagnosis from other branches of biology have been modified for soil-borne plant pathogens. Though very sensitive, most of these techniques are slower and more laborious than the routine inspection of plants for disease symptoms, yet they need less expertise and are consistently accurate. Apart from immunology, most laboratory diagnostic procedures have so far proved ill-suited for field use, as they are neither sufficiently flexible nor portable. Despite the rapid detection and identification of numerous viruses by routine enzyme-linked immunosorbent assays (ELISA), there have been until recently few suitable protocols adapted for fungi. DNA hybridization forms the basis of another group of fairly rapid diagnostic techniques which will probably be restricted to the laboratory for some while yet. Nevertheless, DNA techniques have proved valuable in various investigations, such as unravelling the phylogeny of some species of soil-borne pathogens. For the foreseeable future methods based on antibodies and DNA probes are likely to extend their domination of detection and diagnosis techniques. By making recognition easier, these techniques play complementary roles in expanding our understanding of the biology, taxonomy and ecology of soil-borne pathogens.     

Fertilizers and soil-borne diseases

Abstract. Nutrient manipulation through fertilization or modification of the soil environment to influence nutrient availability is an important cultural control for plant disease and an integral component of production agriculture. Fertilization decreases soil-borne diseases by maximizing the inherent disease resistance of plants, by facilitating disease escape through increased nutrient availability or stimulated plant growth, and by altering the external environment to influence the survival, germination and penetration of pathogens. The flexibility in most disease-nutrient interactions permits a much broader utilization of this cultural control in decreasing disease severity than is presently practised. It is clear that the severity of most diseases can be decreased and the chemical, biological or genetic control of many plant pathogens enhanced by proper fertilization. Breeding nutrient-efficient or disease-tolerant crops and establishing cultivar requirements should further improve production efficiency.     

利用微生物防除根寄生杂草列当

根寄生杂草列当(Orobanche spp.)已经严重制约全球许多地区的农业发展,寻找有效防除措施迫在眉睫。由于列当具有特殊生活史且与寄主关系密切,常规防除杂草措施难以达到理想防效。目前,尚无既能有效防除列当又不对寄主造成危害且便于大规模推广应用的列当防除措施。在众多列当防除措施中,微生物防除越来越引起关注和重视。本文对微生物防除列当的国内外研究进展及防除机理进行了综述。目前,列当生防微生物的研究主要集中在镰刀菌(Fusarium spp.)等列当病原菌和根瘤菌(Rhizobium spp.)等列当寄主植物共生菌上。微生物防除列当的机制主要包括两方面:一是通过产生代谢产物直接影响列当的萌发和生长,或通过降解列当种子萌发诱导物质间接影响列当的萌发;二是通过提高寄主植物自身对列当的抗性间接影响列当的寄生和生长。此外,本文还重点介绍了植物土传病害的土壤拮抗微生物防除列当杂草的可行性及研究进展。植物土传病害病原菌和列当均首先通过在地下侵染作物的根系进而危害作物正常生长,而作物抗土传病害的机理也与抗列当的机理类似。因此,存在于土壤中具有防治植物土传病害能力的微生物可能也具有防除根寄生杂草列当的功能。本团队前期试验从植物土传病害的土壤拮抗微生物中筛选到在盆栽试验中能够有效防除向日葵列当(O.cumana Wallr.)和瓜列当(O.aegyptiaca Pers.)的放线菌各1株,分别为淡紫褐链霉菌(Streptomyces enissocaesilis Sveshnikova)和密旋链霉菌(Streptomyces pactum Bhuyan B.K)。其中,密旋链霉菌的菌剂在田间试验中既降低了瓜列当的出土数量又增加了番茄的产量。总之,微生物是防除根寄生杂草列当的一条有效途径。     

The mechanisms of biological control of plant diseases

Examples of biological control of plant diseases are analyzed to identify the mechanisms by which such control is effected. The evidence supporting the hypothesis that metabolites produced by one organism may inhibit another is presented. The fact that the formation of such a toxic material is an adaptive phenomenon in response to the presence of the inhibited organism is of considerable significance. Failure to compete successfully for suitable substrates is a form of biological control, that probably ranks second in importance. Lysis appears not to be a primary mechanism of microbial antagonism in the soil. Biological control of soil-borne pathogens is an important factor in disease control in nature. Its exploitation requires sustained and imaginative effort.     

土壤学不应忽视对作物土传病原微生物的研究

随着集约化种植程度的提高,管理不善、单一作物连续种植、秸秆还田等因素导致的土传病害日益严重,使作物高产对农药的依赖程度不断提高,对我国农业可持续发展、环境和农产品安全构成了很大的威胁。但是,我国当前土壤学几乎忽视了这一土壤学范畴的研究领域。土传植物病原微生物功能明确,是研究土壤微生物区系和生物多样性与功能、土壤微生物与植物生长、土传病原微生物与拮抗微生物等关系的理想研究对象。土壤学在揭示土传病原微生物的生长规律、控制土传病原微生物数量、发挥拮抗微生物的作用、防治作物土传病害等方面具有独特的优势。深入认识土传病原微生物适宜生长的土壤环境是防控作物土传病原微生物生长,实现农药使用量零增长的基础。解决当前严重的作物土传病害不仅是土壤学的责任和义务,而且可以极大地推动土壤学的发展。     

Interactions between mycorrhizae and diseases caused by soil-borne fungi

Abstract . There are many records of mycorrhizae, particularly ectomycorrhizae, protecting roots against soil-borne plant pathogens, though fungal or viral diseases of the green parts are usually more severe in mycorrhizal plants. There are various mechanisms by which mycorrhizae protect themselves against soil-borne diseases. The occurrence and ecological significance of these mechanisms are discussed in relation to environmental factors. Mycorrhizae will probably become a very effective means of biological control once we have learned how to manage them.     

Estimation of number of root-nodule bacteria by a nodulation-dilution frequency method

Rhizobia spend most of their life in the soil outside the host plants. Soil conditions, therefore, may exert influence on the survival and variation of rhizobia so as to contribute to the nitrogen fixation of the legumes. The knowledge on the ecology of Rhizobium in soils may expected to give basis for the success of seed inoculation and establishment of effective strains in the field. In addition, it will render service for the study of the ecological soil microbiology, for example, ecology of pathogens of soil-borne plant diseases.     

连作根系分泌物加剧土传病害的机制和缓解措施研究进展

基于植物-土壤反馈理论,连作体系中的根系分泌物必然在加剧土传病害发生中起重要作用,但相关研究证据尚缺少系统总结。本文梳理了连作导致土传病害加剧的现象以及连作对典型根系分泌物组分的累积。从有利于土传病原菌由土体向根际迁移、增殖和致病（“利病”）、破坏根际有益微生物群落防线（“压益”）和毒害根系免疫系统（“自毒”）等三个方面,揭示连作根系分泌物中某些物质促进土传病原菌入侵的机制。从根系分泌物角度阐述轮作、间作、套作、伴生和嫁接等多样性种植方式缓解连作土传病害的机制。提出鉴定“利病”、“压益”和“自毒”物质以及构建对应的消减技术途径,可为土传病害绿色高效综合防控提供理论和技术支撑。     

强还原土壤灭菌研究进展

随着经济和技术的快速发展,以高投入高产出、高频种植等为特点的集约化种植已成为我国重要的农业生产模式。伴随集约化种植程度不断提高,作物土传病害频发,且易发生酸化、次生盐渍化、土壤板结等土地退化现象,往往造成作物连作障碍。强还原土壤灭菌方法(reductive soil disinfestation,RSD)作为一种环境友好型方法,兼具杀灭土传病原菌和改善土壤理化性质、易操作和处理时间短等特点,已成功用于作物连作障碍的防治。本文根据不同作物类型及不同土传病原菌,归纳总结了RSD处理过程所采取的有机物质类型、施用量、温度条件、淹水覆膜状况及灭菌效果。     

土壤原生动物 ——研究方法及其在土传病害防控中的作用

原生动物是原生生物的一种,是土壤食物网中的消费者,能捕食细菌和真菌等其他微生物.除了对土壤微生物群落和物质循环产生重要影响外,根际原生动物与细菌、真菌等土壤微生物共同组成生物网络屏障,并在抵御土传病原菌入侵作物根系的过程中发挥着重要作用.然而,相对于根际有益细菌和有益真菌,国内外关于原生动物防控土传病害的效果及作用机制...     

噬菌体靶向消减土壤生物污染的制约因素及提升策略

土壤中存在能够威胁植物、动物和人体健康的病原细菌，消减这类土壤生物污染是一体化健康（One Health）的重要任务。因具有宿主细菌专一性强、侵染效率高、环境扰动性小等特性，噬菌体成为生态消减土壤病原细菌生物污染的重要手段。然而，由于土壤生物和非生物环境的复杂性，提升噬菌体消减土壤生物污染的效果和稳定性仍是当前的重大挑战。本文从噬菌体在土壤中的生存以及与病原细菌互作等过程着手，分析总结影响噬菌体阻控土壤生物污染效果和稳定性的主要因素：1）噬菌体的宿主细菌谱和种群数量，2）土壤病原细菌的多态性，3）影响噬菌体与土壤病原细菌互作的环境因素。通过构建高效噬菌体鸡尾酒、改善噬菌体产品形式和优化噬菌体施用技术等措施，建立提升阻控土壤生物污染效果和稳定性的策略，为完善土壤生物污染噬菌体疗法提供科学支撑。     

药用植物连作障碍研究评述和发展透视

连作障碍作为现代农业生产中较普遍的问题,在药用植物栽培生产中表现尤为严重,据统计约70%以块根类入药的药用植物在种植过程中都存在严重的连作障碍问题。连作障碍已经成为制约药用植物品质和发展的关键性因素。本研究从药用植物连作障碍问题研究现状出发,分析了当前药用植物连作障碍形成的三大共性问题,即根系分泌物诱导根际土壤酸化、根际微生物群落结构失衡和植株病毒病严重,具体体现在:根系分泌物诱导根际土壤微生物差异性演化、土传病原菌的化感互作、根际微生物区系的失衡加大土壤酸化、根际病原菌增多和有益菌减少导致的土存真菌病害加重、病毒病伴生和发展。并分析了土壤灭菌法、功能微生物调控、作物多样性栽培和生物质炭改良的根际调控策略在减缓药用植物连作障碍中的潜在作用。作者呼吁从事连作障碍研究的工作者应重视从根际生态学角度出发,以土壤食物网为切入点,应用现代系统生物学和化学生态学技术与方法,全面系统探究根系分泌物介导下植物-土壤-微生物的相互作用过程与机制,并着重关注土壤线虫和土壤病毒在连作障碍发生发展中的生态位关系,以深入阐明连作介导土壤酸化的生态学机制和病原菌响应根系分泌物的协同进化机理,在此基础上,采用多种根际调控相结合的策略减缓连作障碍问题,全面考虑经济、社会和生态效益,做到"生态预防为主、综合治理为要"。     

Rice (Oryza sativa L.) plant protection using dual biological control and plant growth-promoting agents: Current scenarios and future prospects

Various microorganisms live in association with different parts of plants and can be harmful, neutral, or beneficial to plant health. Some microbial inhabitants of plants can control plant diseases by contesting with, predating on, or antagonizing plant pathogens and by inducing systems for plant defense. A range of methods, including plant growth-promoting microorganisms(PGPMs) as biological control agents(BCAs)(BCA-PGPMs) are used for the biological management and control of plant pathogens. S...     

强还原土壤灭菌防控作物土传病的应用研究

随着集约化种植程度的不断提高,土传病原菌侵染、土壤酸化、次生盐渍化、养分平衡失调等引起的作物连作障碍发生率不断攀升,严重威胁着集约化农业的可持续发展。强还原土壤灭菌(Reductive Soil Disinfestation,RSD)法是一种作物种植前的土壤处理方法,即:在发生土传病害的土壤上,添加大量的易分解有机物料、灌溉、薄膜覆盖或淹水阻隔与大气的气体交换,快速创造土壤强还原环境,短期内杀灭土传病原菌的方法。强还原杀灭土传病原菌的作用机理包括:1)厌气杀灭好氧病原菌;2)还原过程产生有毒有害的物质杀灭土传病原菌;3)强还原改变土壤微生物群落结构,抑制土传病原菌活性。强还原土壤灭菌法还具有提高土壤p H,减轻次生盐渍化的作用,具有广谱性和环境友好性。本文介绍了该方法的起源、作用机理、影响该方法效果的因素及其应用前景。     

作物土传病害防控的健康微生物群落构建原理与实践

植物-土壤反馈效应及农田生产特点决定了农田土壤生产力的不可持续性,因而必须采用适当的措施方可保持地力常新。施用化肥解决了农田土壤的养分贫化问题,极大地提高了作物产量,但激发了土传病原生物的活性,作物土传病频发成为制约集约化农业可持续发展的瓶颈问题。现有的研究成果表明,地上生物多样性与土壤微生物多样性紧密联系,植物提供的有机物质是连接二者的物质基础。单一作物种植的集约化农业提供给土壤微生物可利用的有机物质来源单一,导致土壤微生物多样性下降,削弱对土传病原生物致病性的抑制作用。本文提出,在作物生长过程中添加土壤有益微生物偏好利用的有机物质,激活土壤有益微生物,可能是维持集约化农业土壤生物健康,抑制作物土传病的有效途径。为此,有必要开展各种土壤微生物偏好利用的有机物质以及作物生长过程中如何施用有机物质的方法。     

作物土传真菌病害发生的根际微生物机制研究进展

土传病害是制约我国农业生产可持续发展的重要瓶颈。根际是作物养分高效利用的窗口,是植物-土壤-微生物相互作用的关键微域,也是土传病害发生发展的主要场所。在宏基因组学快速发展的今天,了解根际微生物与土传病害互作关系,有利于从微生物种群、功能代谢和抑病物质等研究找出防控土传病害的有效方法。本文综述了根际微生物与土传真菌病害的发生机制关系,探讨了土传病原真菌致害机理,并提出目前研究的不足和未来研究的重点。目前,我国农业生产中土传真菌病害发生严重,很多是由不同病原菌复合侵染的结果,其致害机理较为复杂。定向优化根际微生物群落结构提升植物根际微生态抗性,是防控土传病害途径之一,应加以重视。现有研究多偏向根际促生微生物,而忽视了根际有害细菌与病害发生和作物生长的关系。今后的研究应系统评估土传真菌病害的发生及危害程度、归类土传真菌病原菌类型、深入研究土传真菌病害发生的根际微生态机理以及研发土传真菌病害综合防控技术。     

强化拮抗菌有机肥在连作大棚草莓上的应用效果研究

采用室内平板培养、气候箱内土壤处理及盆栽和大棚试验相结合的方法,研究了以腐熟中药渣堆肥为原料制备的液体肥料在强化了拮抗微生物前后对草莓枯萎病菌生长的抑制作用及对病害的防治效果,结果表明:普通液肥和两种强化液肥对两种草莓病原真菌的生长都有不同程度的抑制作用;三种液肥经辐照灭菌后均丧失了对病原真菌的抑制作用;两种强化液肥处理土壤10～15d后能显著抑制土壤中草莓枯萎病菌的生长繁殖而降低土壤中病原菌的数量。盆栽试验表明:普通液肥辅照灭菌后对草莓枯萎病仍有一定的防效,但显著低于没灭菌的液肥;两种强化液肥对草莓的盆栽防效显著高于普通液肥。大棚小区试验显示:施用有机液肥的三个处理的草莓产量显著高于常规对照,而发病率显著低于常规对照;分别强化了两种拮抗菌的液肥对病害的防效均好于未强化的液肥;施用液肥对根际土壤酸化和盐分积累有一定的修复效果,使小区草莓增产达93～110%,畸形果率降低23.5%,并对草莓品质有一定程度的改善。强化了拮抗菌的有机液肥对草莓连作障碍的防治效果显著提高。