Diversity and field site variation of indigenous populations of soybean bradyrhizobia in Japan by fingerprints with repeated sequences RS alpha and RS beta

Two hundred and thirteen isolates of soybean bradyrhizobia indigenous to si x field sites in Japan were characterized using hybridization probes RS alp ha, RS beta, nifDK and hupSL from Bradyrhizobium japonicum and indole-3-ace tic acid production to clarify diversity and endemism of their population s tructures. Significant diversities and site-dependent variations were obser ved in terms of Bradyrhizobium species, hup genotype and fingerprints with repeated sequences RS alpha and RS beta. The fingerprints at one site with no history of soybean cultivation were less diverse than those at other sit es. Even within the populations of B. japonicum hup(-) isolates, which were commonly indigenous to the six field sites, several RS alpha copies cluste ring around nif genes were highly conserved. The results suggest that soybe an bradyrhizobia may be diversified in individual fields as associated with host plants and local soil conditions. (C) 1999 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reser ved.