棉花/芥菜套作调控土壤微生物抑制黄萎病的机制及抑病菌筛选

Verticillium wilt is the main disease in cotton, particularly in the continuous monoculture system. Previous studies have shown that intercropping of cotton with mustard can effectively control Verticillium wilt. However, such an intercropping has not been adopted in Xinjiang–the main cotton production region in China - due to difficulties in changing cropping systems and saline-alkaline soils. Understanding the mechanism of cotton/mustard intercropping in controlling Verticillium wilt is critically important for developing and implementing alternative yet effective wilt management strategies. We propose to study the relative importance of several mechanisms for wilt control in the cotton/mustard intercropping systems, including suppressive soil microbiome, and specific beneficial microbes. One key objective is to understand the dynamics of pathogen inoculum within and between seasons in the two cropping systems, helping to explain the inhibitory effect of the intercropping on cotton wilt. Amplicon-based DNA metabarcoding will be used to quantify the dynamics of bacterial and fungal communities in the bulk soil and rhizosphere in the two cropping systems, aiming to identify the key microbial groups that are likely responsible for disease suppressive effects. In parallel, microbes will be isolated from rhizosphere soils, sequenced to confirm that they are those with higher abundance in the intercropping system (associated with healthy cotton plants), and then screened for their effect against V. dahliae. A number of these strains with antagonistic effects against the wilt disease will be combined with other known PGPM (plant growth promoting rhizosphere microorganisms) isolated from rhizosphere in the intercropping system to form a synthetic microbial consortium. The consortium will be test for their persistence and effect against in glasshouse and field conditions. This project will elucidate the mechanism of the suppression of cotton wilt achieved by the cotton/mustard intercropping system from the perspective of microflora and pathogen inoculum dynamics, underpinning the development and application of synthetic microbiome for sustainable disease management.

黄萎病是棉花生产中最重要的土传性病害。我们前期研究发现套作芥菜有效防治棉花黄萎病，但是由于栽培模式和盐碱土壤限制不适用于新疆棉区。研究棉花/芥菜套作调控土壤微生物防治黄萎病的机制，筛选根际可共存的有益菌群替代套作防治土传病害，有望突破生防菌田间效果不稳定的瓶颈。本研究拟通过连续3年田间试验，利用DNA Metabarcoding技术和选择性培养技术，比较研究单作和套作棉田土壤和根际微生物区系演变特征和大丽轮枝菌消长规律，结合生物信息学、传统分离鉴定技术筛选棉花根际抑病菌群，利用标记荧光法验证候选有益微生物与大丽轮枝菌间的互作，通过温室试验单一和混合接菌验证有益微生物在抑病、抑菌、促进植物生长、促进根际存活、定殖和诱导棉花抗病等方面作用，从微生物区系、病原菌和根际有益微生物角度解析套作芥菜调控土壤微生物防治黄萎病的机制，以期为最终实现利用高效有益菌群可持续防治土传病害奠定基础。

黄萎病是棉花生产中最重要且难以防治的土传病害。本研究通过连续3年病圃试验，比较研究棉花单作和套作芥菜土壤中微菌核的动态消长规律；利用扩增子测序技术研究土壤细菌和真菌群落的动态变化，分析套作对土壤微生物区系演变的调控作用；从套作芥菜棉株的根际土壤中分离细菌和真菌，以扩增子测序结果为指导构建了复合菌群，并验证其对棉花的促生作用和对黄萎病的防治效果。取得的主要结果如下：（1）棉花/芥菜套作在连续3年试验中均表现出显著减少土壤中病原菌（P＜0.05），显著降低黄萎病发生（P＜0.01），增加棉花的产量（P＜0.05）；（2）套作芥菜对土壤细菌和真菌群落Alpha多样性无显著影响，但套作芥菜显著改变了棉田土壤细菌群落结构，尤其是在棉花生育期，而对土壤真菌的影响出现在非生育期。（3）Simper分析显示造成套作芥菜和单作处理土壤微生物区系差异的核心物种为：Pseudomonas、Ilumatobacter、Rhizobium、Sphingomonas、RB41、Arthrobacter、Microidium、Fusarium、Talaromyces、Bipolaris和Mortierella。（4）分离获得504株根际细菌和115株根际真菌，共有24株固氮菌、9株解磷菌、2株解钾菌、12株产IAA菌和17株拮抗菌，隶属于Proteobacteria、Firmicutes、Actinobacteria和Bacteroidetes；4株拮抗真菌，隶属Aspergillus、Trichoderma和Fusarium。（5）构建SCI（6株）和SCII（7株）两个复合菌群，对黄萎病的防治效果分别为54.02%和69.31%，此外，SCII成功激活GhPOD等7个棉花关键防御基因的表达。总之，本研究阐明了棉花/芥菜套作调控土壤微生物抑制黄萎病的机制，并在此基础上指导构建了一个多功能生防菌群。本研究丰富和完善了棉花黄萎病的生物防治理论，为制备具有实用价值的生防菌剂提供了材料和依据。研究结果发表SCI论文4篇，培养研究生2名。