番茄根系分泌物抑制青枯病发生的土壤微生物驱动机制

Continuous cropping of tomato frequently caused bacterial wilt. Our previous results showed that tomato root exudates greatly influenced the assemblage of soil bacterial community which may further altered the incidence of tomato bacterial wilt. However, due to the complexity of natural root exudates, the effects of root exudate composition on disease suppression function of rhizosphere microbiome are largely unknown. In this study, we will first synthesize artificial root exudates based on tomato root-secreted carbon sources. We will then test the effects of artificial root exudates on soil microbiome structure (i.e., bacterial abundance, bacterial community composition and microbial activity) by using Miseq amplicon sequencing and quantitative PCR. Additionally, we will test the effects of root exudate composition on soil suppressiveness (i.e., rhizospheric pathogen abundance and bacterial wilt incidence) by conducting pot experiment. Root exudate characteristics and microbial taxa which is responsible for disease suppression will also be determined by applying linkage analyses. Lastly, we will verify the disease suppression ability of soil microbiome by examining its antagonistic ability, resource competition level and induced systemic resistance ability. Our results will help to decipher plant-microbe interactions and provide a theoretical basis for modulating soil bacterial community for suppression of tomato bacterial wilt by applying low molecular weight organic matter.

番茄连作易引发青枯病。申请人前期研究发现番茄根系分泌物可改变土壤微生物群落结构，并可能进一步影响青枯病发生。由于根系分泌物成分复杂，尚不清楚根系分泌物组分如何影响根际微生物群落的抑病功能。本研究以番茄根系分泌碳源模拟复杂的番茄根系分泌物，利用高通量测序和荧光定量PCR技术探究番茄根系分泌物对土壤微生物群落结构（细菌总量、细菌群落组成和微生物群落活性）的影响；采用盆栽试验检测根系分泌物对土壤抑病能力（根际病原菌总量和青枯病发病率）的调控效应；综合以上研究，明确抑制番茄青枯病发生的根系分泌物特征和微生物类群；通过测定根系分泌物募集微生物群落的养分资源利用率、诱导番茄抗病信号途径标志基因表达量和可培养拮抗菌比例阐明根际微生物群落的抑病机制。本研究有助于揭示植物-根际微生物互作机制，为应用低分子有机质调控土壤微生物群落结构进而防控番茄青枯病提供理论依据。

番茄连作易引发青枯病。番茄根系分泌物可改变土壤微生物群落结构，并可能进一步影响青枯病发生。由于根系分泌物成分复杂，尚不清楚根系分泌物组分如何影响根际微生物群落的抑病功能。本研究以番茄根系分泌碳源模拟复杂的根系分泌物，高通量测序和荧光定量PCR结果表明，与糖类和酚酸类物质相比，氨基酸和有机酸可提高土壤细菌总量，降低细菌丰富度，并对细菌群落结构产生较大影响。根系分泌物碳源丰富度与细菌总量无显著相关性，但与土壤细菌多样性呈显著负相关关系，同时碳源种类越多，其对土壤细菌群落结构的影响越大。盆栽试验结果表明氨基酸可显著提高根际青枯菌数量并提高青枯病发病率，而糖类、有机酸、酚酸及碳源丰富度对根际青枯菌数量和青枯病发病率无显著影响。关联分析发现Acinetobacter、Bradyrhizobium、Ferruginibacter等14个属与病害抑制相关，同时氮、氨基酸和有机酸含量较低的根系分泌物可通过提高土壤细菌多样性从而降低青枯病发病率。通过分子和培养技术从群落水平揭示拮抗竞争是土壤微生物抑制番茄青枯病的主要机制。本研究为应用低分子有机质调控土壤微生物群落结构进而防控番茄青枯病提供理论依据。