Interaction analysis of bacterial communities and physicochemical properties in rhizosphere soil of pepper

【Objective】To analyze interaction between pepper rhizosphere soil bacterial community structure and physicochemical properties, which could provide reference for scientific prevention and control of soil-borne diseases and high yield and high quality cultivation of pepper. 【Method】In this study, the rhizosphere soils of pepper plants at seedling stage(SD), flowering stage(FR), and fruiting stage(FT) were investigated. The pH, organic matter, total nitrogen, alkaline nitrogen, total phosphorus, available phosphorus, total potassium, and available potassium contents in three soil samples were determined. High-throughput sequencing using the Illumina HiSeq 2500 platform was performed to analyze the bacterial Alpha diversity indexes, relative abundance at phylum and genus levels in the rhizosphere soils of pepper plants at different growth stages. Principal coordinate analysis(PCoA) and dissimilarity analysis based on Bray-Curtis distance was conducted to assess the bacterial communities among different growth stages and the correlation with physicochemical factors. 【Result】The results showed significant differences in pH and alkaline nitrogen content among SD, FR and FT as pepper plants grew(P<0.05, the same below). The Alpha diversity indexes, richness and Chao1 index of soil bacterial communities in the three growth stages showed no significant differences(P>0.05). The SD soil had the highest number of unique operational taxonomic units(OTUs). Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, and Cyanobacteria were dominant phyla in the rhizosphere soils of the three growth stages. Streptophyta, Acidovorax, Nitrososphaera and Gp6 had relatively high abundance in the SD rhizosphere soil. Streptophyta, Nitrososphaera and Rhodoplanes had relatively high abundance in the FR rhizosphere soil. Streptophyta and Trinickia were dominant genera in the FT rhizosphere soil. Principal coordinate analysis(PCoA) and dissimilarity analysis revealed significant differences among bacterial communities in rhizosphere soil samples from different growth stages. The correlation analysis showed extremely significant and strong positive correlation between pH and alkaline nitrogen with bacterial communities(P<0.01).【Conclusion】The physical and chemical properties of pepper rhizosphere soil and the structure of bacterial community vary with different growth stages. PH and alkaline nitrogen are key factors influencing the change in bacterial communities.