Genomic diversity of Bradyrhizobium strains compatible with soybean (Glycine max L. Merr.) harboring various Rj-genes

Based on the different sequence of putative Rj-gsn gene reserved in Bradyrhizobium strains, which was concerned with the compatibility between some Rj-genotype soybeans and some Bradyrhizobium strains, the classification depended on sequence of genomic DNA of Bradyrhizobium strains of each nodulation type was thought possible to analyze by the method of restriction fragment length polymorphism (RFLP). Different rare-cutting enzymes Ase I, Dra I, Spe I and Xba I were chosen in order to ideally produce fragments greater than 200 kbp. The dendrogram of Ase I was shown that type C strains were found mainly in one of two clusters, and type B strains in the other cluster. The type A strains were found in both clusters at similar frecuency. The dendrogram by Dra I was split into three clusters, and the type B and C strains were found exclusively in different cluster. The third cluster had all three types almost uniformly. That of Sph I formed small cluster containing type B strains, but it was recognized no tendency that each nodulation type strains formed cluster. That of Xba I was split into two clusters, and one cluster was split into two subclusters. However, this dendrogram was not clarified in the difference between two clusters in compared with that of Dra I. The results of cross-agguligation reaction between each nodulation type strains with the antiserum of those typical strains indicate that strong cross-reaction was observed between some strains of type A and B in this experiment. Also, weak cross-reaction was known between some strains of type A and C (Ishizuka et al., 1991). These experimental results indicated that the type B strains were distantly related to the type C strains in regard to the structure of genomic DNA and that of surface of rhizobial cell, the type A strains were located intermediate between type B and C.