Phylogeny and diversity of Bradyrhizobium strains isolated from the root nodules of peanut (Arachis hypogaea) in Sichuan, China

Twenty-two rhizobial strains isolated from the root nodules of two Chinese peanut cultivars (Arachis hypogaea L. Tianfu no. 3 and a local cultivar) gr owing at four different sites in the Sichuan province, Southwest-China, wer e characterized by growth rate, rep-PCR, PCR-RFLP of 16S rDNA, partial sequ encing of ribosomal genes, and fatty acid - methyl ester analysis (FAME), a nd compared with strains representing Bradyrhizobium japanicum, B. elkanii and other unclassified Bradyrhizobium sp. All peanut isolates from Sichuan were bradyrhizobia. Dendrograms constructed using the rep-PCR fingerprints grouped the strains mainly according to their geographic and cultivar origi n. Based on PCR-RFLP and partial sequence analysis of 16S rDNA it appears t hat peanut bradyrhizobial strains from Sichuan are similar to peanut strain s from Africa and Israel, and closely related to B. japonicum. In contrast, analysis of FAME data using two-dimensional principal component analysis i ndicated that Bradyrhizobium sp, (Arachis) were similar to, but slightly di fferent from other bradyrhizobia. The presence and level of fatty acid 16:1 w5c was the distinguishing feature. The results of PCR-RFLP of the 16S rRN A gene, the partial sequence analysis of 16S rDNA, and FAME were in good ag reement.