番茄青枯病抑病土壤根际微生物群落特征及其抑制性传递机制

Characteristics of Rhizosphere Microbial Communities in a Diseasesuppressive Soil of Tomato Bacterial Wilt and Its Disease-suppressive Transmission Mechanism

根际微生物在宿主植物抵御土传病害发生过程中发挥着重要作用。为探究抑病土壤与感病土壤根际微生物群落特征及其微生物群落构建机制,分别采集抑病土和感病土中的番茄根际土壤,采用实时荧光定量PCR技术检测两种根际土壤中的病原菌含量,并利用16S rRNA基因扩增子高通量测序技术分析抑病和感病土中番茄根际土壤微生物群落多样性、组成、结构以及基于零模型的微生物群落构建机制的差异。结果表明,与感病土相比,抑病土壤中番茄的青枯病病情指数明显降低(病情指数分别为47.5和22.5),其根际中细菌群落具有更高的alpha多样性、更丰富的放线菌门、厚壁菌门以及芽孢杆菌科和链霉菌科等有益微生物,较低的青枯病菌丰度(病原菌丰度降低了12.22倍)并伴随着较高的随机性过程,因此抑病土壤受病害胁迫的适应性较强。将感病土壤与抑病土壤按照一定比例进行混合,形成了仅有感病土D10H0、感病土与抑病土质量比为1︰1的D5H5以及仅有抑病土D0H10这三种处理以进一步检测抑病土壤抑病特性的可传递性。结果表明,随着抑病土比例的增加,番茄青枯病病情指数逐步降低,D10H0、D5H5和D0H10的病情指数分别为41.67、29.17与16.67,而细菌alpha多样性增加,厚壁菌门、链霉菌科和芽孢杆菌科等丰度明显增加,随机性过程的主导作用加强。综上,病害胁迫对番茄根际微生物群落的多样性、组成、结构和群落构建过程产生了显著影响,而抑病土壤能通过植物根系招募有益微生物来抵御病害胁迫。

【Objective】Microorganisms in the rhizosphere play an important role in the process of plants resistance to soil-borne diseases.This study investigated the characteristics of rhizosphere microbial community and the mechanism of microbial community assembly in disease-conductive soil and disease-suppressive soil in a tomato-cultivated field.【Method】Real-time quantitative PCR was applied to detect the pathogen density in disease-conductive rhizosphere soil and disease-suppressive rhizosphere soil.Also,the distinction of tomato rhizosphere soil microbial community diversity,composition,structure,and assembly processes based on zero model were analyzed through high-throughput sequencing of 16S rRNA gene amplicon.【Result】Results show that,compared to disease-conductive soil,there was a significantly lower disease index of tomato bacterial wilt in disease-suppressive soils(disease index in disease-conductive soil and disease-suppressive soil were 47.5 and 22.5,respectively).The rhizosphere bacterial communities in disease-suppressive soils were characterized with higher alpha diversity,more abundant beneficial microorganisms,such as Actinobacteria,Firmicutes,Bacillaceae,and Streptomycetaceae,lower abundance of Ralstonia solanacearum(abundance of pathogenic bacteria decreased by 12.22 times)and accompanied with more stochastic processes.This shows that the adaptability of disease-suppressive soil to pathogenic disease stress was stronger than that of disease-conductive soil.The disease-conductive soil and disease-suppressive soil were mixed in a certain proportion to form three treatments;disease-conductive soil alone(D10H0),a mixture of disease-conductive soil and disease-suppressive soil with a mass ratio of 1︰1(D5H5),and disease-suppressive soil alone(D0H10)to test the transmitability of inhibition properties of disease-suppressive soil.It was observed that with the increase in the proportion of disease-suppressive soil,the disease index of tomato bacterial wilt gradually decreased(the disease index in D10H0,D5H5,and D0H10 were 41.67,29.17,and 16.67,respectively).While the diversity of bacterial alpha gradually increases,the abundance of Firmicutes,Streptomyces,and Bacillaceae increase significantly.Also,the dominant role of the stochastic and random processes is strengthened.【Conclusion】Disease stress had a significant effect on the alpha diversity,composition,structure,and community assembly process of the tomato rhizosphere microbial community.The disease-suppressive soil can recruit more beneficial microorganisms through plant roots to resist pathogenic disease stress.