云南两个花魔芋主产区软腐病害植株腐烂球茎中的菌群组成及特征

Composition and characteristics of microflora in the corm of Amorphophallus konjac K. Koch infected by soft rot in two main konjac production areas in Yunnan

摘要:

【目的】软腐病是侵染魔芋的主要病害，其危害性严重，广泛传播会导致花魔芋绝产，尚无有效防控措施。魔芋软腐病的发生及暴发性传播与病原菌及其菌群有较大相关性。本研究旨在明确云南2个主产区的软腐病害花魔芋球茎及其根际土壤中的主要致病菌和优势微生物种类，分析其菌群结构特征，从而为花魔芋软腐病害的防控提供支撑。【方法】研究采集云南富源和永平2个产区的花魔芋软腐病样品，应用Illumina NovaSeq 6000测序平台进行微生物宏基因组测序和分析。同时采用选择性培养基、多级纯化培养技术以及电镜超微形态解析，分别对病害腐烂球茎中的致病菌及优势菌类进行分离鉴定和观察验证。【结果】两个花魔芋主产区软腐病害植株球茎及土壤中的微生物都非常丰富，共检出107门2 502属15 721种微生物。这2个产区的花魔芋软腐病害主要致病菌均为胡萝卜软腐坚固杆菌(Pectobacterium carotovorum)，此病原菌与嗜麦芽寡养单胞菌(Stenotrophomonas maltophilia)的优势生长是2个产区软腐病害植株腐烂球茎中菌群的主要特征。此外，同产区的病害组织与土壤样品之间的菌群组成差异较大，但这2类样品中的优势菌群组成的区域性差异较小。【结论】两个花魔芋主产区软腐病害球茎组织中菌群与该区土壤菌群的相关性较低，土壤菌群区域性差异比相应的病害组织菌群区域性差异要大。因此，主要病原菌和共生菌的优势生长突破了产地差异影响，成为了病害组织菌群的主要特征，使得2个主产区软腐病害花魔芋球茎中的微生物生态系统具有高度相似性。

Abstract:

[Objective] Soft rot is the main disease of Amorphophallus konjac K. Koch in konjac production areas. Crop failure can be caused by the wide spreading of soft rot, because the serious destructiveness of the disease can not be effectively prevented and controlled at present. The occurrence and explosive spreading of soft rot are closely related to the microflora and pathogenic bacteria in konjac. This study explored the main pathogenic bacteria and dominant microbial species in rotten corms and rhizosphere soil, and analyzed the structural characteristics of microflora in the samples infected by soft rot in two main konjac production areas of Yunnan, aiming to provide theoretical support for the prevention and control of soft rot in konjac production. [Methods] The konjac samples infected by soft rot were collected from Fuyuan and Yongping in Yunnan. The Illumina NovaSeq 6000 platform was used for metagenomic sequencing, and the sequencing data were analyzed. Meanwhile, the pathogenic bacteria and dominant microorganisms in the rotten corms were isolated by multistage purification using selective medium, and observed by an electron microscop. [Results] Large quantities of microorganisms were detected in the rotten corms of diseased konjac from the two main production areas, including 15 721 species that belonging to 2 502 genera of 107 phyla. Pectobacterium carotovorum was the main pathogen in all of the diseased samples infected by soft rot. The main characteristic feature of microflora in rotten corms was that the abundances of pathogen and Stenotrophomonas maltophilia were higher than all the other microorganisms. The composition of microflora present great differences between diseased tissue samples and soil samples, in the same production area, whereas, the microflora composition in the diseased tissue samples or soil samples had slight differences between the two production areas. [Conclusion] The microflora composition showed low correlations between the diseased corm and rhizosphere soil, in the two production areas. The regional difference of microflora in soil was larger than that in the diseased tissue. The results showed that the dominant pathogens and saprophytes played a key role in forming the microflora structure by breaking through the regional impact, and resulted in the microbial ecosystems in the konjac corms infected by soft rot were highly similar in two main production areas.