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  土壤学报  2021, Vol. 58 Issue (4): 814-824  DOI: 10.11766/trxb202003230038
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引用本文  

韦中, 沈宗专, 杨天杰, 等. 从抑病土壤到根际免疫:概念提出与发展思考. 土壤学报, 2021, 58(4): 814-824.
WEI Zhong, SHEN Zongzhuan, YANG Tianjie, et al. From Suppressive Soil to Rhizosphere Immunity: Towards an Ecosystem Thinking for Soil-borne Pathogen Control. Acta Pedologica Sinica, 2021, 58(4): 814-824.

基金项目

国家自然科学基金项目(42090060, 41922053, 42007025和42007038)和国家重点研发计划项目(2018YFD1000800)资助

通讯作者Corresponding author

沈其荣, E-mail: qirongshen@njau.edu.cn

作者简介

韦中(1985—), 男, 安徽临泉人, 博士, 教授, 研究领域: 微生态与根际健康。E-mail: weizhong@njau.edu.cn
从抑病土壤到根际免疫:概念提出与发展思考
韦中, 沈宗专, 杨天杰, 王孝芳, 李荣, 徐阳春, 沈其荣    
江苏省固体有机废弃物资源化高技术研究重点实验室, 作物免疫学重点实验室, 国家有机类肥料工程技术研究中心, 江苏省有机固体废弃物资源化协同创新中心, 南京农业大学资源与环境科学学院, 南京 210095
摘要:作物土传病害已经成为集约化农业可持续发展中的瓶颈,在粮食安全、资源高效和生态健康多目标协同发展的指导思想下,系统的绿色防控理论和技术体系构建是破解该难题的重要前提。作为植物-土壤互作的热点区域,根际栖息着较土体土壤更丰富的微生物群落,是土传病原物入侵作物根系的必经之路。根际微生态系统中的植物、土壤、微生物组和病原物之间的交互作用必然影响着植物健康。笔者将根际微生态系统抵御土传病原物入侵的现象和能力,称之为“根际免疫”。本文重点梳理根际免疫概念形成的4个重要阶段:(1)抑病土壤概念的提出与发展;(2)抑病微生物筛选与作用机制;(3)抑病土壤核心微生物组及互作机制;(4)根际免疫概念的形成与发展思考。最后从关注根际微生态、注重学科交叉和系统揭示根际免疫机制三方面进行展望,以期为提升土壤-植物系统健康和实现农业可持续发展提供理论依据和技术支撑。
关键词土传病害    抑病土壤    根际    微生物组    根际免疫    
From Suppressive Soil to Rhizosphere Immunity: Towards an Ecosystem Thinking for Soil-borne Pathogen Control
WEI Zhong, SHEN Zongzhuan, YANG Tianjie, WANG Xiaofang, LI Rong, XU Yangchun, SHEN Qirong    
Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Key Laboratory of Plant Immunity, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
Abstract: Soil-borne diseases have become a limiting factor for the development of sustainable intensive agriculture. To coordinate the integrative development of food security, resource efficiency, and ecological health, the construction of a systematic theory and integrated approach is vital for sustainably controlling soil-borne pathogens. As a hotspot where plants and soil closely interact, the rhizosphere inhabits diverse microbiomes. Since the rhizosphere is the only way for soil-borne pathogens to penetrate plant roots, interactions between soil, plants, microorganisms, and plant-pathogens harbored in the rhizosphere could affect pathogen invasion and plant health. Recently, the ability of the rhizosphere to act against the invasion of soil-borne pathogens was defined as "rhizosphere immunity". In this review, we introduced this concept in four important stages: 1) the proposal and development of the concept of disease-suppressive soil, 2) the isolation of beneficial microorganisms and their mechanisms in controlling diseases, 3) the deciphering of the structure and function of core microbiomes in disease-suppressive soil, and 4) proposal and development of the concept rhizosphere immunity. Firstly, it was observed that soil microorganisms together with soil abiotic factors determine the ability of soil suppressiveness. Also, previous researchers isolated the key microorganisms and uncovered the underlying mechanisms in disease suppression. Secondly, typical mechanisms including antagonism, nutritional competition, parasitism, predation, induced systemic resistance, and interference of pathogenic signals of pathogenic microorganisms were revealed. In addition to beneficial fungi and bacteria, bacteriophages and protists have also been applied to control pathogens. Despite soil microorganisms playing an important role in disease suppression, application of a single beneficial biocontrol agent into the field usually did not achieve the goal of disease suppression because of its weak colonization ability in the rhizosphere. Therefore, deciphering the composition and functional characteristics of core microorganisms involved in disease suppression has become the hotspot during the past ten years. Thirdly, the core microbial groups and functional genes associated with disease suppression and the approaches to decipher the core microbiomes were identified. Given that the interactions between core microbiomes or with the pathogens are still difficult to verify in natural soil, we reviewed the use of synthetic microbial communities to overcome this limitation. Finally, the background of the concept of "rhizosphere immunity" was introduced. We expounded on the four core functions of rhizosphere immunity: prevention, recognition, response, and homeostasis. Consequently, we used the application of bio-organic fertilizer as an example to demonstrate that rhizosphere immunity could be improved. In the perspective and conclusion section, we appeal with researchers to pay more attention to the belowground micro-ecology, embrace interdisciplinarity, and underly the key mechanisms of rhizosphere immunity. This review could provide a theoretical basis and technical support for improving the health of the soil-plant system and in achieving the aims of sustainable development of modern agriculture and food security.
Key words: Soil-borne disease    Disease-suppressive soil    Rhizosphere    Microbiome    Rhizosphere immunity    

土传病害是指由生活史中一部分或大部分存在于土壤中的病原物(病原细菌、病原真菌、病原卵菌、病原线虫等)在条件适宜时萌发并侵染植物根系而导致的病害。随着集约化农业高速发展,单一作物连作及氮肥、农药等化学品过量施用等因素导致的土传病害日益严重,环境和农产品安全以及农业可持续发展受到了很大的威胁。以土传青枯病(致病菌为青枯菌Ralstonia solanacearum)为例,该细菌性土传病害在我国仅3个省及地区(西藏、内蒙古、澳门)未报道,淮河以南尤为严重[1]。尤其在全球变暖以及集约化农业快速发展的背景下,土壤中植物病原物的风险将会进一步增大[2]。长久以来,植物病理与保护、农学、园艺、土壤、植物营养、微生物等领域工作者均参与到土传病害的研究与防控中,所开发的抗病品种、化学农药和熏蒸、嫁接、轮作、营养平衡、生物菌剂和生物有机肥等单一和综合措施对土传病害的有效控制做出了重要贡献,但当前及未来土传病害的防控形势依然面临着巨大压力[3-4]。相对于地上部植物病害,由于土壤物理、化学和生物环境的复杂性,土传病害的发生和防控更加复杂。从土壤学角度阐释土传病害发生的机制,揭示土壤各因子对土传病害防控的影响,系统梳理各个学科领域的优势,将相关理论和技术体系进行整合,将有助于科研工作者有效解决土传病害问题。

大量研究[5-7]表明,土壤物理、化学和生物学特性均影响着土传病害的发生。根际是受植物根系机械作用及其分泌物显著影响的土壤微域,其物理、化学和生物学特性与土体土壤显著不同。根际是土传病原物入侵作物根系的必经之路[8],必然受定殖在该区域复杂多样的微生物的影响。为此,根际这一特殊微域中植物、土壤、微生物组、病原物之间的交互作用必然显著影响植物健康。笔者将上述四者在根际互作形成的抵御土传病原物入侵的现象和能力,称之为“根际免疫”(rhizosphere immunity)[9]。本文重点梳理根际免疫概念形成的4个重要方面或阶段(图 1):(1)抑病土壤概念的提出与发展;(2)抑病土壤微生物筛选与作用机制;(3)抑病土壤核心微生物组及互作机制;(4)根际免疫概念的形成与发展思考。在此基础上,呼吁关注根际微生态、注重学科交叉并系统揭示根际免疫机制,以期为提升土壤-植物系统健康和实现农业可持续发展提供理论依据和技术支撑。

图 1 根际免疫概念发展、代表工作及重要贡献 Fig. 1 The development of rhizosphere immunity concept, representative work, and contributions
1 抑病土壤概念的提出与发展

虽然Atkinson[10]于1892年就已报道存在抑制棉花枯萎病发生的土壤,且于1931年指出土壤微生物与土壤的抑病能力有关[11],但直至1974年才由Baker和Cook[12]首次提出抑病土壤(disease suppressive soil)的概念,明确其定义为“土壤中病原物不能定殖,或能定殖但危害很小或无危害,或能定殖并一时造成危害但随后即使在病原物存在的情况下发病也很轻的土壤”。与之相对应的是非抑病土壤,也称感病土壤(disease conducive soil),指容易感病的土壤。自此,先后在多种作物及多种土传病害发生的农田系统中证实了抑病土壤的存在。依据病原物的不同,目前已有以下四种类型的抑病土壤:(1)抑制细菌性病害发生的抑病土壤,如土豆疮痂病链霉菌[13]、番茄青枯病[14]的抑病土壤;(2)抑制真菌性病害发生的抑病土壤,如小麦全蚀病[15]、香蕉枯萎病[16-17]、豌豆根腐病[18]、花菜立枯病[19]的抑病土壤;(3)抑制线虫病害发生的抑病土壤,如莴苣根结线虫[20]、桃根结线虫[21]的抑病土壤;(4)抑制原生生物病害发生的抑病土壤,如根肿病[22]的抑病土壤。值得注意的是,田间抑病土壤可能会呈斑块化特征,即在同一田块会出现某些健康的植株周围全是发病植株的现象[23]。研究[23-24]发现在斑块化抑病土壤中细菌和原生动物群落以及它们的互作在抑病中发挥着重要作用。

自1931年Henry[11]提出微生物是抑病土壤的基础之一后,大量研究通过土壤加热灭菌、使用杀菌剂、土壤移植等方式逐渐证实微生物参与了抑病土壤的形成与功能维持[25-30]。如Mendes等[26]将甜菜立枯病的抑病土壤按照10%的比例与感病土壤混合后,再次种植甜菜后,立枯病的发病率显著降低;而经50 ℃加热灭菌1 h后再次种植甜菜发现,该土壤丢失了抑病能力,导致立枯病发病率显著升高。尽管抑病土壤的物理化学性状,如pH、有机质含量、黏粒含量可直接作用于病原物而提升土壤抑病能力[31-32],但它们更多则是通过影响土壤微生物的装配而间接作用于病原物,进而提升土壤抑病能力[33]。因此,抑病土壤的形成与功能维持是由土壤中生物与非生物因素共同决定的[27]

2 抑病土壤微生物筛选与作用机制

明确微生物在抑病土壤形成与功能维持中的重要作用之后,大量研究开始探索抑病土壤的微生物学作用机制。根据抑病机制的不同,抑病土壤一般分为广谱抑病(general suppression)和特异抑病(specific suppression)土壤[29]。广谱抑病能力的形成通常与土壤中较高的微生物活性有关,其抑病能力不能转移,可因土壤有机质的增加而提升[34]。特异抑病能力是由于土壤中某类微生物主导形成的,可转移性是其主要的特征。当接种一定比例的特异抑病土壤至感病土壤中后,感病土壤能逐渐转化为抑病土壤[35]。因此,挖掘抑病土壤中发挥抑病作用的有益微生物及其作用机制,为土传病害的防控提供微生物资源与理论指导,成为研究的热点。

抑病土壤中诸如假单胞菌(Pseudomonas[15, 26]、链霉菌(Streptomycete[36]等有益细菌,木霉(Trichoderma[37]、非致病性镰刀菌(non-pathogenic Fusarium[38]等有益真菌以及病原细菌的专性噬菌体[39]等多种功能微生物被陆续分离筛选出来,随后有益微生物通过拮抗和营养竞争、寄生、捕食、诱导植物抗性以及干扰病原物致病信号等方式抑病的机制也逐渐被揭示(图 2)。例如,假单胞菌通过产生2, 4-二乙酰基间苯三酚、吩嗪、吡咯菌素及氰酸等物质拮抗病原物从而提升土壤的抑病能力[27, 40-41]。芽孢杆菌通过分泌脂肽类物质、表面活性剂以及小分子挥发性物质(volatile organic compounds,VOCs)等直接杀灭病原物或抑制病原物,从而提升土壤的抑病能力[42-45]。Gu等[46]研究发现,铁载体介导的根际细菌与病原青枯菌的铁营养竞争决定着番茄青枯病的发生与否,在育苗阶段加入高产且铁载体不会被病原青枯菌“窃取”的有益微生物,可有效保护作物健康。此外,诸如假单胞菌、芽孢杆菌等有益微生物还可通过水杨酸途径或茉莉酸途径等激发植物的系统抗性,提升根际抑病能力[47]。一些芽孢杆菌还可通过干扰病原物之间的交流信号,进而降低病原物的致病能力[48]。有益真菌通过寄生机制能有效抑制核盘菌、尖孢镰刀菌、立枯丝核菌等病原真菌的侵染[49-51]。以具寄生能力的哈茨木霉4742为例,该菌株通过Nox1介导产生高浓度的过氧化氢(H2O2)以及金属肽酶NMP1并分泌至胞外,协助木霉菌捕食尖孢镰刀菌,满足自身菌丝的延伸进而实现对病原真菌的寄生作用,最终提升了根际抑病能力[50-51]。除了有益真菌和细菌,学者们还分离了大量病原细菌的专性噬菌体[52-53],这些噬菌体能够特异性侵染病原细菌,进而降低病原细菌数量以及生长和致病能力[39]。原生动物也可通过捕食或产生具有抑菌作用的代谢产物等机制抑制病原细菌的根际入侵[54]。总体而言,大量土壤有益微生物的分离及其作用机制的揭示为理解根际复杂的菌群互作和抑病机制奠定了基础。

图 2 有益微生物抑制植物土传病害发生的机制 Fig. 2 Mechanisms of beneficial microorganisms in suppressing soil-borne plant diseases
3 抑病土壤核心微生物组及互作机制

土壤微生物在抑病中发挥重要作用,但田间实践研究[55]表明单一有益菌常因根际定殖能力不强而无法实现稳定抑病的目标,说明在实际抑病土壤中可能是多个核心微生物协同发挥抑病作用。为此,解析抑病土壤核心微生物的组成及功能特征成为当前的研究前沿和热点。自2010年以来,随着16S/18S/ITS扩增子测序(16S/18S/ITS-amplicon sequencing)、宏基因组(metagenomic)、宏转录组(metatranscriptomics)、宏蛋白组(metaproteomics)和宏代谢组(metabolomics)、DNA稳定性同位素示踪(DNA stable isotope probing)、基因芯片技术(phyloChip/geochip)等多组学研究技术的发展,抑病土壤核心微生物组结构和功能解析不断取得突破(图 3)。例如,甜菜立枯病[26]、香蕉枯萎病[16]、草莓枯萎病[36]、小麦全蚀病[56]等抑病土壤的核心微生物组被解析出来。次生代谢产物合成、胁迫响应等与抑病相关的核心功能基因也被挖掘出来[23, 57]。上述研究表明,土壤抑病能力与土壤微生物的核心菌群结构和功能密切相关,但不同区域、不同病害的抑病土壤核心微生物组成与功能存在显著差异。因此,利用多组学技术解译抑病核心微生物组仍是抑病土壤研究领域的一大重点。

图 3 抑病土壤核心微生物组的结构与功能解析 Fig. 3 Deciphering the structure and function of core microbiome in disease suppressive soils

尽管组学技术能解析出自然菌群中潜在的核心抑病菌群,但它们协同抑制病原物的机制很难用自然菌群来验证。为此,近年来学者们利用合成微生物群落探究群落互作及协同抑病机制(图 3)。Li等[58]基于合成菌群,发现相对于便利型菌群,竞争型的微生物群落有利于抑制病原细菌的入侵。Wei等[59]及Hu等[60]分别从营养竞争和拮抗竞争的角度进一步阐述了合成菌群抵御病原细菌入侵根际的机制,指出功能菌群在营养资源利用上的互补效应和在拮抗物质抑菌中的协同效应,对合成菌群的抑病能力起关键作用。Durán等[61]通过宏基因组、宏培养组学(分离筛选大量细菌和真菌)和合成菌群的方法阐述了细菌和丝状真菌之间的跨界竞争互作对作物抵御真菌和卵菌等植物病害的影响。Wang等[39]通过构建特定病原细菌的噬菌体组合,发现噬菌体可通过靶向消灭病原细菌,降低其生存竞争能力,同时还可重新调整根际土壤菌群的结构,恢复群落多样性,增加群落中具有拮抗能力的有益菌丰度,进而提升根际菌群抑制病原细菌入侵的能力。此外,Wang等[62]人工构建了噬菌体和有益细菌的组合,通过寄生和竞争双胁迫抑制了病原青枯菌的生长,有效抵御了土传青枯病的发生。

4 根际免疫概念形成与发展 4.1 根际免疫的提出背景

尽管科学家已开发出环境友好的方法以控制植物土传病害,如生物农药、抗性植物品种、土壤改良方法和微生物接种剂等,但上述策略大多仍是孤立的应用,导致其效果不能充分体现。经过近50年的发展,尤其是“土壤记忆”(soil memory)[63]及“土壤遗留效应”(soil legacy)[64]等概念提出以后,抑病土壤的内涵、边界等方面均有了质的变化。学者们研究[65-66]发现,病原物入侵后通过激活植物系统诱导抗性,富集多种特异性的根际有益菌,而这些有益菌相互合作并作为一个整体可共同参与抵抗植物病原物;且上一代受到病原物入侵的植株通过土壤遗留效应协助下一代植株抵御同种病原物的入侵。上述复杂的植物-土壤-微生物组-病原物互作关系,让人们逐渐认识到抑病土壤的实质是植物、土壤、微生物组和病原物四大因子在根际交互作用的结果。Wei等[9]提出的根际免疫是将根际作为一个生态系统或者“超有机体”(meta-organism),强调整个根际微生态系统抵御病原物入侵的能力,其核心是根际形成了能够抵御土传病原物入侵和维持植物健康能力的特定微生物群落(图 4)。值得注意的是,近期Zhang等[67]提出的根际免疫(rhizospheric immunity)是以植物为中心,主要从植物本身根组织和细胞出发,重点阐述延伸蛋白(主要在植物根部表达的细胞壁糖蛋白)与边界细胞共同形成“根细胞外陷阱”网络等根际免疫在植物防御中的重要作用。两个概念有很好的互补作用,丰富了根际免疫的内涵。

图 4 根际免疫构成、互作机制及驱动因素 Fig. 4 The components of rhizosphere immunity, their interactions, and the driving factors
4.2 根际免疫的四个功能

根际免疫是植物先天免疫系统的外延,是植物适应多胁迫环境的一种必然选择。根际免疫具有经典免疫理论中的四个核心功能:预防、识别、响应和稳态[9]。预防是根际有机体整体限制病原物进入根际生态系统或者在根际有限增殖的基础能力;如果病原物可克服根际物理、化学和生物屏障并在根际中开始繁殖,其特殊的生理活动会被根际微生物组识别,如病原细菌的噬菌体;一旦识别,病原物的存在会触发一系列响应,如植物的响应(包括细胞凋亡和防御化合物如胼胝质的产生)、微生物组水平的响应(某些微生物拮抗性状的表达增强,抗生素产量的显著增加)。如果拮抗菌在病原物根除后进入休眠状态(例如,形成芽孢或孢子),就可能会形成防御库,可在重新感染后迅速重新激活,从而为根际提供获得性免疫记忆。除了发现和抑制病原物外,面对非生物和生物胁迫时的根际系统的稳态平衡也是根际免疫的一项基本功能。根际免疫系统会降解衰老或垂死的生物细胞(来自根或微生物)以及可能对根际系统产生负面影响的污染物和农药残留。需要说明的是,根际免疫的四个功能仍需要大量研究证据来支撑,亦或需要对根际免疫概念作进一步扩充和完善。

4.3 基于施用含生物类有机肥的根际免疫调控技术

根际免疫的核心是在根际形成了能够抵御土传病原物入侵根系的特定微生物群落,因此,可通过调控根际微生物区系,进而在作物当季快速获得土壤免疫能力,实现土传病害的有效防控。自2003年以来,国内不少科研团队,将传统的有机肥与特定的功能微生物组合起来,研发出防控青枯病、枯萎病等土传病害的生物类有机肥(生物有机肥或复合微生物肥),并开发了营养钵育苗等配套施用技术。一系列研究表明,施用这些生物类有机肥不仅能提升土壤有机质、调节土壤pH等,进而直接抑制土传病原物在根际的增殖,更能调控土壤微生物区系结构和功能,激发土著有益菌群的增殖、驱使菌群互作关系趋于竞争型,进而抑制土传病原物的入侵,最终有效控制番茄、香蕉、西瓜、黄瓜、香草兰等重要经济作物土传病害的发生[33, 68-72],产生了显著经济和社会效益。为了进一步提升生物类有机肥的抑病效果和稳定性,近几年,基于生物多样性-生态系统功能理论模型和微生物群落成员的互作关系,构建了高效抑制土传病害发生的有益微生物群落[23, 39, 46, 58-59],建立了有益微生物群落构建的基本原则,为开发复合有益功能生物有机肥及其协同增效因子提供理论基础和技术支撑。总体而言,利用生物类有机肥调控根际土壤微生物区系结构和功能,提升根际免疫能力,进而保障作物健康和生态环境安全具有重要的实践意义。

5 思考与展望

在全球变暖、人类活动加剧和土传病害日益严重的背景下,开发新型、综合、高效的可持续土传病害阻控策略,对实现生态环境保护和食物安全高效生产的多目标需求至关重要。根际免疫作为一个整体的概念框架,以生态系统理论为基础,综合以植物、土壤、微生物组和病原物等为中心的土传病害管理理论和技术措施,强调不仅要独立了解根际免疫的每个组成部分,更要解析各组成部分如何相互作用和影响(图 4),并客观评估它们对根际免疫和植物健康的贡献。为了实现上述目标,需要从事不同学科领域的工作者分工协作,促进多学科合作,探明根际免疫相关科学问题,推动不同学科知识和理念的相互交融和应用。

5.1 根际免疫呼吁关注人类活动对根际微生态的影响

关于土传病害的发生,人们的认知在逐步丰富和深入。病三角(disease triangle)强调了自然生态系统中寄主植物、病原物、环境三个因素的相互作用。根际免疫将环境拆分为土壤和微生物组两部分,强调了微生物组与植物及病原物互作对病害发生的影响。在农业生态系统中,病三角加上人类农业生产活动因素则构成了“病四面体”(disease tetrahedron)。在这个四面体中,人类干预作用对土传病害发生的影响越来越大,甚至是起到了主导作用。人类活动不仅仅表现在对宿主植物的驯化、改造(嫁接、基因工程等)和对病原物的非特异性杀灭抑制(化学农药和熏蒸等)等方面,更多的是对植物生长环境的改变,比如小气候的调控(光照、水分、CO2等)、土壤养分供应(施肥)、植物种群密度设置(高复种指数)及生态多样性控制(除草)等。根际免疫将人们对土传病害认知的焦点转移至地下,呼吁关注地下微生态互作以及它们在土传病害发生与阻控中的重要作用,探明人类活动所产生的区域环境改变以及全球变化对植物、土壤、微生物组和病原物以及它们之间(尤其在根际这一微域)互作的短期和长期影响。

5.2 根际免疫呼吁多学科的交叉合作

现有土传病害发生与阻控相关的概念以“病三角”某一构成因子为中心。比如,植物先天免疫、呼救系统(cry for help,相当于获得性免疫)等是以植物为中心的概念;抑病土壤、土壤记忆、土壤遗留效应、土壤免疫响应等强调了土壤及土壤微生物的重要性;化学农药、熏蒸等则是以杀灭病原物为中心的抑制策略,忽略了这一措施对土壤生态系统功能的影响。上述理论概念或者技术方法仅仅抓住了某一个重心,虽然实现了重要突破,但由于忽视了系统中的其他组成份的重要性,加上领域方向差异的原因,限制了理论概念向其他学科方向的外延,也降低了应用的广泛性。根际免疫则以根际为中心,融合了各领域相关概念的核心观点,便于不同领域间的交流,有利于各方协作解决实际生产问题。根际免疫呼吁通过人为干预,提高土壤生物多样性,在减少病原物数量、削弱其致病性的同时,保持和提高植物的抗病性;调整播种期,改变耕作方式和栽培技术,优化土壤生态环境,创造有利于寄主生长发育而不利于病原扩增、繁殖的条件,以达到控制病害的目的。

5.3 根际免疫亟需深入广泛的创新研究

需要指出的是,根际免疫概念框架尚不成熟,亟需国内外不同领域学者进一步探究、丰富和完善。以下从植物、病原物、微生物组、环境以及精准调控等角度,提出一些与根际免疫相关的科学问题,供读者和相关科研工作者参考。

(1)植物与根际免疫:不同植物品种或者基因型根际免疫差异的驱动因素是什么?比如探明影响植物激素合成、氮磷养分吸收等关键基因介导的根系分泌物、根际微生物组与根际免疫能力之间的关系。

(2)病原物与根际免疫:土壤中病原真菌、病原细菌、病原卵菌、根结线虫等单独或混合侵染对根际免疫及植物健康有什么影响?它们在单独或复合入侵根际中与根际其他生物有哪些互作,这些互作对根际免疫的形成有哪些贡献?

(3)微生物组与根际免疫:以往重点研究了根际细菌组和真菌组在根际免疫中的重要作用,以后需要关注根际原生动物组、病毒组、线虫组等以及它们与细菌、真菌形成的多营养级微食物网互作在抵御土传病原物入侵中的作用机制。

(4)环境与根际免疫:尽管之前已有不少关于土壤理化环境与土传病害发生之间的关系,但是尚缺少全球变化以及人类活动干扰,如温度、CO2浓度升高或者氮肥施用对植物、病原物和微生物组三者互作以及根际免疫的影响。

(5)根际免疫精准调控:目前以生物有机肥为代表的土壤抑病性调控研究取得了一系列突破,但也存在根际微生物组调控方向不明确、效果因种植制度和土壤环境变化而不稳定的问题。未来亟需构建更加精准的根际免疫调控策略,比如靶向抑制病原物、定向提升核心功能微生物的功能等技术措施。

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