桑树青枯病发生的根际微生态作用机制

Guangxi is the largest region of sericulture production in China, and in order to acquire high leaf yield, long-term single nitrogen fertilizer was applied in mulberry, which resulted in the changes of soil physical and chemical properties, soil microbial diversity decreased and the occurrence of bacterial wilt was very serious. The related survey showed that using resistant varieties and organic fertilizer could adjust soil micro-ecological environment, and the soil itself could be adjusted to suppress bacterial wilt. Aiming at the above issues, the soil proteomics and microbial community structure were studied systematically using iTRAQ (isobaric tags for relative and absolute quantitation) proteomics research methods and high-throughput sequencing technology. In the meantime, root exudates components, soil enzymes and physical and chemical properties were detected. The above study could reveal the relationship between the changes of microbial community structure and root exudates and the occurrence of bacterial wilt. The micro-ecology mechanism of application organic fertilizer to improve the resistance of bacterial wilt was clarified by adding different root exudates components and soil fumigation sterilization. The results of this study could provide a theoretical basis for the prevention and control of bacterial wilt and reasonable fertilization in mulberry.

广西是蚕桑生产第一大省区，蚕农为了追求产叶量，常期过量偏施氮肥，造成土壤理化性质发生改变，土壤微生物多样性降低，青枯病发生严重。而相关调查表明，采用抗青枯病桑树品种及增施有机肥调节土壤微生态环境，利用土壤自身的调节可起到抑制青枯病的目的。本项目针对以上问题，以根际微生物及根系分泌物为研究切入点，利用同位素标记相对和绝对定量（iTRAQ）蛋白质组学研究方法和高通量测序技术，系统研究青枯病不同抗性桑树基因型及不同施肥措施桑树根际土壤蛋白质组及微生物种群结构变化规律，同时检测根系分泌物组分及土壤酶等理化指标的变化，明确微生物种群结构及根系分泌物组分等指标变化与青枯病发生的相互关系。采用盆栽试验及模拟供试桑园土壤，通过添加差异根系分泌液组分及土壤熏蒸灭菌等方法，阐明施用有机肥提高桑树青枯病抗性的根际微生态作用机制。

广西是我国蚕桑生产第一大省区，蚕农为了追求产叶量，常期过量偏施氮肥，造成土壤理化性质发生改变，土壤微生物多样性降低，青枯病发生严重。有研究表明采用抗青枯病桑树品种以及增施机肥可调节土壤微生态环境，起到抑制青枯病的目的，但是土壤微生态环境调控青枯病发生的内在机制并不清楚。本项目以根际微生物及根系分泌物为研究切入点，系统研究桑树根际土壤微生态环境与青枯病发生的关系。通过本项目的实施，揭示了抗青枯病基因型桑树植株的根际土壤微生物丰度和对碳源的利用能力均高于感青枯病基因型植株，其根际微生物群落结构也相对稳定，同时土壤蛋白质组差异分析表明抗青枯病基因型桑树根际土壤中氨基酸和抗生素合成代谢活跃，利于有益菌群富集，在一定程度上抑制了青枯病的发生。开展了不同施肥措施下桑树根际微生态环境变化规律研究，证实施用有机肥可使桑树根际土壤微生物丰度、多样性和均匀度以及碳源利用能力提高，基因型差异对根系分泌物带来的影响要大于施肥带来的影响。通过研究差异根系代谢物（氨基酸）对桑树生长和根际土壤的调控，明确了亮氨酸添加处理在增加植株生物量、提高叶片各种品质、改善土壤微生物群落结构方面都有积极作用。本研究为桑树青枯病的防治提供了理论基础，为桑园土壤微生态环境的改善提供了思路。课题按照计划顺利进行，取得了丰富的研究成果。