Diversity of indigenous Bradyrhizobium strains isolated from three different Rj-soybean cultivars in terms of randomly amplified polymorphic DNA and intrinsic antibiotic resistance

Diversity of indigenous Bradyrhizobium strains isolated from three differen t Rj-genotypes of soybean (Glycine max L. Merrill) cultivars which was inve stigated based on randomly amplified polymorphic DNA (RAPD) fingerprinting, intrinsic antibiotic resistance (IAR) and indole-3-acetic acid (IAA) produ ction, was correlated with preference for and compatibility with Rj-genotyp es of soybean cultivars for nodulation. Seventeen strains from Akishirome ( non-Rj), 22 strains from CNS (Rj(2)Rj(3)) and 19 strains from Fukuyutaka (R j(4)) were isolated. All of the isolates from Akishirome and Fukuyutaka and 8 isolates from CNS formed effective nodules on each Rj-soybean cultivar, while 14 isolates from CNS did not form effective nodules on Fukuyutaka aft er inoculation under sterile conditions. The 14 isolates from CNS produced IAA. Cluster analysis based on RAPD fingerprinting using 5 primers revealed the presence of two clusters, A and B. Cluster B contained B. elkanii USDA 61, USDA 76 and indigenous bradyrhizobia of 14 isolates from CNS showing I AA production and cluster A contained B. japonicum USDA 110, A1017 and indi genous bradyrhizobia not showing IAA production. Indigenous bradyrhizobia s trains in cluster A were further divided into 3 subclusters, A-1, A-2, and A-3 different from the cluster of B. japonicum USDA 110 and A1017. Identity of subclusters between RAPD fingerprinting and IAR phenotype was not compl etely obtained. Subclusters A-1, A-2, and A-3 consisted mainly of isolates from Akishirome, CNS, and Fukuyutaka, respectively. Preferences of bradyrhi zobia for Rj-soybean cultivars for nodulation may be estimated by genetic d iversity at the strain level.