Effects of Continuous Cropping on Bacterial Community Structure in Rhizospheric Soil of Sweet Potato

Background: Continuous cropping obstacles from sweet potato are widespread, which seriously reduce the yield and quality, cause certain economic losses. Bacteria of Rhizospheric soil are the richest and are associated with obstacles to continuous cropping. However, few studies on how continuous sweet potato cropping affects the rhizospheric soil bacterial community structure. In the study, Illumina Miseq method was used to explore rhizosphere soil bacterial community structure changes with different sweet potato varieties, and the correlation between soil characteristics and this bacterial community after continuous cropping, to provide theoretical guidance for prevention and treatment of sweet potatoes continuous cropping obstacles. Results: After continuous cropping two years, the results showed that (1) the dominant bacterial phlya in rhizospheric soils from both Xushu18 and Yizi138 were Proteobacteria, Acidobacteria, and Actinobacteria. The most dominant genus was Subgroup 6_norank. The relative abundance of rhizospheric soil bacteria of two sweet potato varieties changed significantly. (2) The richness and diversity indexes of bacteria in Xushu18 rhizospheric soil were higher than those from Yizi138 after continuous cropping. Moreover, the beneficial Lysobacter and Bacillus were more prevalent in Xushu18, but Yizi138 contained more harmful Gemmatimonadetes. (3) Soil pH decreased after continuous cropping, and redundancy analysis result indicated that soil pH was correlated significantly with bacterial community. Spearman’s rank correlations coefficients analysis demonstrated that pH was positively associated with Planctomycetes and Acidobacteria, but negatively associated with Actinobacteria and Firmicutes.Conclusions: After continuous cropping, the bacterial community structure and physicochemical properties of sweet potato rhizospheric soil were unbalanced, and the changes from different sweet potato varieties were different. The contents of Lysobacter and Bacillus were higher in the sweet potato variety resistant to continuous cropping. It provides a basis for developing new microbial fertilizer for sweet potatoes to alleviate continuous cropping obstacle.