有益菌群高效抑制土传青枯菌入侵番茄根际的机制：铁载体效应的研究

Previous study showed that beneficial microbial community could increase plant resistance to Ralstonia solanacearum (Rs) due to species and functional diversity. Moreover, we found siderophore productivity of microbial community had significantly positive effect on Rs inhibition. However, the mechanism of siderophores mediating interactions between beneficial microbial community and Rs has not been fully disentangled. Therefore, we are going to investigate mechanisms of siderophores as drivers of species interactions by using four beneficial bacteria and constructing them into gradient communities. In order to understand interactions within beneficial community and between beneficial community and Rs driven by siderophores, the project will be carried on through three aspects via microcosms. Firstly, interactions within beneficial community will be studied by measuring community productivity. Additionally, sampling and complementarity effects will be evaluated via comparing productivity of monocultures and whole communities. Secondly, mechanisms of interactions between beneficial community and Rs driven by siderophores will be demonstrated by comparing contributions of siderophore productivity and relative affinities to iron, separately. Third, effects of siderophore on reduction of Rs virulence will be determined by measuring virulence genes expression. Finally, we are going to verify species interactions in vivo and obtain optimal combination of beneficial community on resisting Rs. This project will provide knowledge of mechanisms of siderophores as drivers of interactions between beneficial community and Rs in the rhizosphere. The results will give guidelines on better selection of beneficial community with high biocontrol efficiency.

有益菌群因物种及功能多样性可提高番茄青枯病的生防效率。申请人前期发现，有益菌群产铁载体能力与其对青枯菌的抑制作用存在显著正相关，但铁载体介导的土壤微生物间互作机制尚未清楚阐明。本研究以4株从番茄根际获得的有益菌为材料，通过构建有益菌群落，从有益菌间、有益菌群-青枯菌间互作关系两个角度，考察铁载体介导的微生物互作关系及其对青枯菌致病功能的影响。研究内容利用微孔板系统从以下3个方面展开：①探明铁载体介导有益菌间的互作关系，评价群落内各物种的贡献大小；②通过考察有益菌群与青枯菌铁载体产量及其对铁的相对亲和力，阐明铁载体抑制青枯菌生长的机制；③通过考察青枯菌致病相关基因的表达，揭示铁载体影响青枯菌致病能力的分子机理。最终利用组培瓶限菌系统验证物种互作关系，并获得最佳的有益菌组合。本项目为阐明根际条件下有益菌群-青枯菌间互作关系及其分子机制、构建高效抑制病原青枯菌的有益菌组合提供理论依据。

由土传病原菌引起的作物土传病害是制约全球粮食优质高产和农业可持续发展的重要因素，作物根际微生物群落是抵御土传病原菌入侵作物根际的天然屏障，根际微生物与病原菌之间对有限营养资源的激烈争夺影响着土传病害的发生。在根际环境中生物有效铁资源十分匮乏，微生物分泌铁载体及其介导的铁素营养利用和竞争方式在调控根际细菌与病原菌互作中可能发挥着重要的作用。本项目以土传番茄青枯病病原菌—茄科劳尔氏菌（Ralstonia solanacearum，简称青枯菌）为模式病原菌株来验证根际细菌铁载体产生及其对土传青枯病发生的影响。结果发现：. 1）铁载体介导铁素吸收在微生物互作方面发挥重要作用。限铁加剧有益菌群对病原菌的作用，其中主要原因是由于铁载体的产生、作用形式和强度取决于菌株种类。在营养竞争型有益菌群中，铁载体对菌群互作的影响更加显著。. 2）铁载体介导营养竞争型有益菌群对病原青枯菌的直接作用能够预测有益菌群防控青枯病的能力，而铁载体介导的菌群互作强度也与菌群的防控效果有良好的相关性，说明有益菌群产生的铁载体可影响土传病原菌的生长，同时铁载体也可介导营养菌群间的互作对菌群的抗病发挥作用。. 3）分泌铁载体是根际细菌普遍存在的代谢特征。与在富铁条件下相比，限铁条件下根际细菌对青枯菌的生长具有更为强烈的影响（促进或者抑制），铁载体介导的根际细菌对青枯菌生长的作用解释了总代谢物质介导作用的76%，铁载体是驱动根际细菌与青枯菌相互作用的重要因子。.