Genotypic Diversity among Strains of Bradyrhizobium japonicum Belonging to Serogroup 110

Thirty-three strains of Bradyrhizobium japonicum within serogroup 110 were examined for genotypic diversity by using DNA-DNA hybridization analyses. The analysis of the DNA from 15 hydrogen-uptake-negative strains with the bradyrhizobial uptake hydrogenase probe pHU52 showed variation in degree of homology and restriction fragment length polymorphism of EcoRI-restricted DNA. Clustering analysis of the 33 strains on the basis of DNA-DNA hybridization analysis with four restriction enzymes and with the bradyrhizobial nodulation locus, pRJUT10, as probe indicated the existence of four groups of strains, which were less than 70% similar. Restriction digestion of genomic DNA with BamHI and DNA-DNA hybridization with pRJUT10 permitted classification of each of the strains according to a specific fingerprint pattern.