Bradyrhizobium ivorense sp. nov. as a potential local bioinoculant for Cajanus cajan cultures in Côte d'Ivoire

For many smallholder farmers of Sub-Saharan Africa, pigeonpea (Cajanus cajan) is an important crop to make ends meet. To ascertain the taxonomic status of 19 pigeonpea isolates of Côte d'Ivoire previously identified as bradyrhizobia, the representative strains CI-1BT, CI-14A, CI-19D and CI-41S were characterized by a polyphasic approach. Phylogeny of 16S ribosomal RNA (rRNA) genes placed these nodule isolates in a separate lineage from the 21 species of the B. elkanii super clade, and close to B. elkanii USDA 76T, B. pachyrhizi PAC48T, B. ripae WR4T and B. tropiciagri SEMIA 6148T type strains. In phylogenies of concatenated partial dnaK, glnII, gyrB, recA and rpoB sequences, the C. cajan isolates again formed a separate lineage, with strain CI-1BT sharing 95.2% as the highest sequence similarity with B. tropiciagri SEMIA 6148T. Comparative genomic analyses corroborated the novel species status, with 86% ANIb and 89% ANIm as the highest average nucleotide identity (ANI) values between strains CI-1BT and B. elkanii USDA 76T.