有机土壤微生物群落演替与土传病害抑制机理的研究

In China, the first long term greenhouse experiment for studying organic vegetable production was set up at Quzhou experimental station in 2002, comprising of organic, integrated and conventional farming systems. Recently, it was observed that microbial biomass and densities of earth worms was higher in the organic farming system than those in the other two systems, while the severities of several plant diseases were lower. The accelerated succession of microbial communities possibly due to the huge amount of organic fertilizer applied and enhanced activities of earthworm could be responsible for diseases suppression in the organic system. Here, we propose a research project to study the interaction between the succession of microbial communities or populations known containing several antagonists (Pseudomonas and Actionbacteria) and the abundance of three pathogens (Ralstonia Solanacearum, Verticillium dahlia and Phytophthora Capsici) causing soil borne plant diseases via a comprehensive sets of metagenomic methods (high throughput sequencing, PCR-DGGE and q-PCR). This approach allows us to study the succession of microbial communities associated with soil borne diseases-suppression in an organic farming soil. Microcosm and greenhouse experiments were planned to further explore how did different ratios of organic soil, organic fertilizer or earth worms affect the succession of microbial communities and survive of these three phytopathogens in soils. The proposed study could shed lights on the mechanisms of microbial community succession for suppressing soil borne diseases, which is a prerequisite for harnessing microbial community to control soil borne diseases.

始于2002年的河北曲周实验站日光温室定位试验是国内率先开展的有机蔬菜生产的长期系统的定位研究。结果显示：长期有机生产体系下植物病害的严重度比无公害和常规体系下显著降低，或与土壤微生物种群的演替相关。为探索土壤微生物群落的演替与土壤抗病性的作用机理，本项目拟采用前沿的宏基因组分析技术(高通量测序、PCR-DGGE)系统地研究定位试验中有机、无公害和常规土壤中全细菌和关键拮抗菌（Pseudomonas 和 Actionbacteria）群落的演替与土传病原物（细菌青枯菌、黄萎病菌和辣椒疫霉菌）种群动态的相关性。进一步采用控制条件下的microcosm和温室实验研究不同比例的有机土壤、有机肥或蚯蚓活动对土壤微生物种群的演替、土传病原物种群动态及植物病害的影响。上述研究将首次系统地研究有机体系下微生物种群的演替抑制土传病害的机理，为合理利用土壤微生物抑制土传病害提供方法指导和理论依据。

本项目基于曲周有机蔬菜长期定位实验，系统研究了有机种植对土壤微生物、根际微生物结构和功能的影响，分析了有机土壤微生物组对辣椒疫病和番茄青枯病的抑制效果。（1）发现长期有机农业种植提高了土壤质量，改变了土壤微生物种群，富集了寡营养型和难利用碳源降解微生物（Ignavibacteria和Acidobacteria Gp6）菌群，降低了氨氧化细菌和古菌的相对丰度。上述结果表明有机农业影响了土壤中介导碳氮循环的微生物，该部分结果2019年发表于FEMS Microbiology Ecology（Ding et al., 2019）。（2）有机土壤微生物组具有抑制蔬菜土传病害的能力，其中辣椒疫病的发病率分别较综合或常规土壤微生物组处理的辣椒低41.3％和34.1％，番茄青枯病的发病率较综合和常规处理分别低55.0%和60.9%。进一步结合拮抗菌的分离培养、根际微生物组分析和复合型拮抗菌剂回接实验，发现长期有机土壤微生物组通过强化根际芽孢杆菌的拮抗性抑制上述两种土传病害，该部分结果发表在Frontiers in Microbiology（Li et al., 2019）。（3）通过根袋和高通量测序实验，发现拮抗芽孢杆菌在根系的空间分布特征；通过健康根际微生物组继代培养实验，发现无法通过育种的模式选育健康根际微生物组，该部分结果将进行进一步丰富完善，争取形成更大的成果。综上所述，本项目揭示了Bacillus 拮抗性的提高是有机土壤微生物组抑病的关键机理，为构建抑病微生物组提供了一定的理论基础。