Bradyrhizobium nanningense sp. nov., Bradyrhizobium guangzhouense sp. nov. and Bradyrhizobium zhanjiangense sp. nov., isolated from effective nodules of peanut in Southeast China

Abstract Nine slow-growing rhizobia isolated from effective nodules on peanut ( Arachis hypogaea ) were characterized to clarify the taxonomic status using a polyphasic approach. They were assigned to the genus Bradyrhizobium on the basis of 16S rRNA sequences. MLSA of concatenated glnII-recA-dnaK genes classified them into three species represented by CCBAU 53390 T , CCBAU 51670 T and CCBAU 51778 T , which presented the closest similarity to B. guangxiense CCBAU 53363 T , B. guangdongense CCBAU 51649 T and B. manausense BR 3351 T , B. vignae 7-2 T and B. forestalis INPA 54B T , respectively. The dDDH and ANI between the genomes of the three representative strains and type strains for the closest Bradyrhizobium species were less than 42.1% and 91.98%, respectively, below the threshold of species circumscription. Effective nodules could be induced on peanut and Lablab purpureus by all representative strains, while Vigna radiata formed effective nodules only with CCBAU 53390 T and CCBAU 51778 T . Phenotypic characteristics including sole carbon sources and growth features supported the phylogenetic results. Based on the genotypic and phenotypic features, strains CCBAU 53390 T , CCBAU 51670 T and CCBAU 51778 T are designated the type strains of three novel species, for which the names Bradyrhizobium nanningense sp. nov., Bradyrhizobium guangzhouense sp. nov. and Bradyrhizobium zhanjiangense sp. nov. are proposed, respectively.