Bradyrhizobium lablabi sp. nov., isolated from effective nodules of Lablab purpureus and Arachis hypogaea

Abstract

Five strains isolated from root nodules of Lablab purpureus and Arachis hypogaea grown in the Anhui and Sichuan provinces of China were classified as members of the genus Bradyrhizobium. These strains had identical 16S rRNA gene sequences which shared 99.48 %, 99.48 % and 99.22 % similarity with the most closely related strains of Bradyrhizobium jicamae PAC68^T, Bradyrhizobium pachyrhizi PAC48^T and Bradyrhizobium elkanii USDA 76^T, respectively. A study using a polyphasic approach, including 16S rRNA gene RFLP, IGS-RFLP, BOX-PCR, comparative sequence analysis of the 16S–23S rRNA intergenic spacer (IGS) and the recA, atpD and glnII genes, DNA–DNA hybridization and phenotypic tests, showed that the five strains clustered into a coherent group that differentiated them from all recognized species of the genus Bradyrhizobium. Sequencing of nifH and nodC genes and cross-nodulation tests showed that the representative strains CCBAU 23086^T, CCBAU 23160 and CCBAU 61434, isolated from different plants, had identical nifH and nodC gene sequences and were all able to nodulate Lablab purpureus, Arachis hypogaea and Vigna unguiculata. Based upon these results, the name Bradyrhizobium lablabi sp. nov. is proposed for this novel species and strain CCBAU 23086^T ( = LMG 25572^T = HAMBI 3052^T) is designated as the type strain. The DNA G+C mol% is 60.14 (T _m).