RESUMEN
Thirty-four rhizobium strains were isolated from root nodules of the fast-growing woody native species Sesbania virgata in different regions of southeast Brazil (Minas Gerais and Rio de Janeiro States). These isolates had cultural characteristics on YMA quite similar to Azorhizobium caulinodans (alkalinization, scant extracellular polysaccharide production, fast or intermediate growth rate). They exhibited a high similarity of phenotypic and genotypic characteristics among themselves and to a lesser extent with A. caulinodans. DNA:DNA hybridization and 16SrRNA sequences support their inclusion in the genus Azorhizobium, but not in the species A. caulinodans. The name A. doebereinerae is proposed, with isolate UFLA1-100 (=BR5401, =LMG9993=SEMIA 6401) as the type strain.