香蕉抑病型根际微生物区系形成机制研究

Banana long-term monoculture destroyed the soil microbial community, thus leading to a serious soil-brone Fusarium wilt disease. Manipulation of soil microbiome is one of the most important ways to control this banana soil-brone Fusarium wilt disease, while the ultimate aim for soil microbiome manipulation is making the rhizosphere microflora to be suppressive to this disease. Previous work done by the applicant has been confirmed that the rhizosphere microbes in one banana orchard with a low Fusarium wilt disease incidence in Hannan Island showed an excellent suppressiveness to the disease. However, it is still unclear about what kind of beneficial microbes were assembled in the disease-suppressive rhizosphere, which were recruited from the bulk soil at different banana growth stages. In this research program, MiSeq high-throughput sequencing and qPCR technique will be used to decipher the microbial community in the disease-suppressive rhizosphere at different banana growth stages by field and greenhouse experiment. And how the banana root exudates at different growth stages collected from the disease-suppressive orchard drives rhizosphere microbiome assembling will be studied by pure culture experiment. Furthermore, how microbial community in disease-suppressive rhizosphere response to Fusarium oxysporum f. sp. cubense race 4 invasion will also be explored in our program. This program is very important for ascertaining the key time point and factor for disease-suppressive rhizosphere formation of the banana orchard with a low Fusarium wilt disease incidence, and is also very vital for elucidating the mechanism of rhizosphere microbiome assemblage in disease-suppressive soil mediated by root exudates. Finally, this project will provide the theoretical guidelines for overcoming the biological obstacle of banana continuous cropping.

香蕉长期连作致使土壤微生物区系失衡，导致土传枯萎病发生严重。土壤微生物区系调控是防控香蕉土传枯萎病的重要手段之一，而形成抑病型根际微生物是区系调控的最终方向。申请人前期工作已证实海南某低发枯萎病蕉园能形成抑病型根际微生物区系，但此香蕉根际在不同生育期从土体土壤中具体招募了何种微生物进行组装而形成此抑病型微生物区系亟待研究。本项目拟利用MiSeq高通量测序技术辅以实时荧光定量qPCR技术，通过田间定位及室内培养试验，解析不同生育期香蕉抑病型土体及根际微生物区系的特征，揭示不同生育期香蕉根系分泌物如何驱动抑病型根际微生物的组装，并探究香蕉抑病型根际抵御尖孢镰刀菌侵染的微生物生态学过程。本项目拟探明抑病型根际形成的关键时期和关键因子并阐明根系分泌物介导下的香蕉抑病型根际微生物区系的形成机制，最终为防控香蕉连作生物障碍提供理论指导。

香蕉土传枯萎病的爆发严重制约了我国乃至世界“卡文迪许”香蕉产业的发展。抑制香蕉土传枯萎病发生的土壤微生物区系的形成机制解析及其抵御尖孢菌的微生态机制仍有待深入研究。本项目主要研究了抑病型土壤上所种植的香蕉形成的根际土壤及不同植株组织的微生物区系特征及土壤代谢组与抑病能力的相关性。此后进一步研究了抑病型土壤微生物区系多样性对微生物区系装配的影响以及装配后的微生物区系抵御尖孢菌入侵的影响。最终，研究了土壤初始理化属性对抑病型土壤微生物区系装配的影响。主要结果如下：从土体至根际、根、茎、叶群落多样性指数逐渐下降。各生态位可培养细菌组成分析表明假单胞菌平均相对丰度及其对群落差异贡献度较高，抑病型蕉园假单胞菌数量和种类更多，铜绿假单胞菌、香茅醇假单胞菌、黄褐假单胞菌、香鱼假单胞菌、台湾假单胞菌、P. lutea、及P. rhizosphaerae为抑病蕉园特有假单胞菌。抑病型土壤代谢组分析表明中棕榈酸单甘油酯、单硬脂酸甘油酯、甲胺、磷酸盐和木糖与土壤抑病能力的形成有关。抑病型土壤微生物多样性与微生物区系装配的结果表明，随着所培育微生物区系细菌丰富度的降低，土壤抑制尖孢菌入侵的能力下降；抑病型土壤中噬几丁质菌科、噬纤维菌科、粘球菌科和草酸杆菌科以及鞘脂杆菌科与抵御尖孢菌入侵能力显著相关。不同多样性抑病型土壤微生物区系与尖孢菌入侵关系的研究结果表明，细菌多样性高的群落通过提高群落中物种之间协同关系所占的比例，增强了抵御尖孢菌入侵的能力，具有降解真菌细胞壁能力的马赛菌属等关键微生物是抵御尖孢菌的入侵的关键微生物。抑病型土壤初始的理化性状对土壤微生物群落的装配起着驱动作用，装配形成的微生物区系中溶杆菌属、鞘氨醇单胞菌属、链霉菌属等是抑制尖孢镰刀菌入侵的关键微生物类群。本项目的研究对于解析抑病型土壤微生物区系的形成机制具有一定的理论指导意义，同时，构建的可培养微生物资源库为调控连坐土壤形成抑病型土壤提供了生物资源。