Effects of different concentrations of phosphorus on microbial communities in soybean rhizosphere grown in two types of soils

Microbial communities in plant rhizosphere interact in a complicated manner among soil types, plant genotypes and soil environmental conditions. In this study, the effects of phosphorus (P) nutrition on microbial community structures in soybean rhizosphere were examined in a pot experiment. Soybean genotypes of Dongsheng 1 and Suinong 14 grew in two kinds of sand/soil (4:1, v/v) mixed cultural media with application of three P levels of P0 (0 mg kg−1), P1 (15 mg kg−1) and P2 (40 mg kg−1). The bacterial and fungal communities in soybean rhizosphere at the start of the pod stage (R3) were examined based on the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) banding patterns of partial 16S rDNA and 18S rDNA ITS regions and sequencing methods. Principal component analysis based on DGGE banding patterns showed that the soil type was the dominant factor in changing both bacterial and fungal communities in the soybean rhizosphere. However, separated principal component analysis based on individual soil showed that the microbial community structures were also influenced by soybean genotypes and soil P concentrations, and the influences of P were greater than those of genotypes. BLAST search of sequence data generated from excised DGGE bands indicated that bacteria belonging to Proteobacteria, Actinobacteria, Verrucomicrobia, Bacteriodetes and Gemmatimonadetes, and fungi belonging to Ascomycetes and Basidiomycetes commonly inhabited the soybean rhizosphere.