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

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.