RESUMO
Many researchers consider the use of different probes for hybridization assays as suitable for studying the genetic diversity of nitrogen fixing bacteria. In this study for asessing genetic diversity among Bradyrhizobium japonicum isolates, two different probes [sucA and topA] chosen from the chromosomal genome of Bradyrhizobium strain USDA 110 were designed, evaluated by DNAMAN software and implemented in the DNA/DNA hybridization of eighteen isolates. Hybridization patterns of the sucA and topA probes showed that all B. japonicum isolates were clustered into 4 and 5 groups, respectively. It was also found that the sequences of these genes among the isolates were different, thus making them suitable for studying the genetic diversity of rhizobial bacteria. The sequence diversit of topA gene was more variable than that of the sucA gene