Abstract:

To explore the microbial community structure and soil type suitable for pepper cultivation through the changes of the community structure of different soil rhizosphere microbes after pepper planting, we used the pepper (Capsicum annuum) SJ11-3, an inbreed line, as the material, and conducted the high throughput RNA-seq sequencing via Illumina MiSeq 2500 sequencing platform on the rhizosphere microorganisms from three different types of soil (fluvo-aquic soil, paddy soil and yellow-brown soil) after cultivating pepper with uncultivated soil as control. Using bioinformatics analyses, we evaluated the abundance indexes and the diversity indexes from the V3+V4 region of 16S rRNA gene of soil bacteria and the ITS1 region of soil fungi as well as the soil microbial community structure. The results showed that a total of 2253 bacterial Operational Taxonomic Units (OTUs) and a total of 775 fungal OTUs were obtained in control while a total of 2353 bacterial OTUs and a total of 877 fungal OTUs were obtained after planting pepper. Planting pepper caused the increase of bacterial OTUs and fungal OTUs in the three different types of soil and the number of OTUs unique to fluvo-aquic soil was significantly higher than those unique to paddy soil and yellow-brown soil before and after cultivating pepper. In addition, we also found that the relative abundances of bacterial genus, including Rhodanobacter, Gemmatimonas, Bradyrhizobium and Sphingomonas etc., and the fungal genus, including Fusarium and Penicillium etc., were significantly increased in three types of cultivated pepper soil. Meanwhile, the analyses of the microbial community species abundance indexes (ACE and Chao1 indexes) and the microbial community species diversity indexes (Shannon and Simpson index) indicated that planting pepper caused the significant increase of the fungal Shannon index but significant decrease of Simpson index in fluvo-aquic soil, paddy soil and yellow-brown soil. However, the bacterial community diversity indexes did not change significantly. The results indicated that cultivating pepper could cause significant influence on the changes of the microbial community diversity, the relative abundances and type of OUT in soil, and enhance the growth and reproduction of bacterial genus and fungal genus in soil. Among the three types of soil, after planting pepper, the microbial community structure in fluvo-aquic soil was healthier and no large enrichment of pathogenic bacteria was observed. However, in paddy soil and yellow-brown soil, the enrichment of pathogenic bacteria easily occurred. Thus, we recommend fluvo-aquic soil as the suitable type for cultivating pepper.

Key words: pepper cultivation, soil microbial community structure, bacterial community structure, fungal community structure, species diversity, community diversity