Genetic grouping of Bradyrhizobium strains compatible with soybean (Glycine max L. Merr.) harboring Rj-gene by AFLP-fingerprinting analysis

Soybean (Glycine max L. Merr.) cultivars form nodules on roots by infection with Bradyrhizobium strains. However, soybean cultivars harbor nodulation conditioning genes, Rj ₂, Rj ₃ and Rj ₄ form ineffective nodules with some strains of Bradyrhizobium. These strains were classified into nodulation-types A, B and C through their compatibility with Rj-gene. The type B was incompatible with Rj ₂-Rj ₃- cultivars while the type C was incompatible with Rj ₄-ones. The type A was compatible with both Rj ₂Rj ₃-and R ₄- cultivars. In this study, in order to examine the relationship between phenotype (nodulation type) and genotype of Bradyrhizobium strains for nodulation, genotyping of Bradyrhizobium strains of each nodulation type was performed and classified by AFLP (Amplified Fragment Length Polymorphism) fingerprinting. On this dendrogram, two clusters could be distinguished at a similarity level of 77%, and the cluster I was divided into 4 sub-clusters. The sub-cluster la had types A and B, and the sub-cluster Ib had types A, B and C. The cluster II had types A and C. These results were similar to that of a RFLP analysis performed in our laboratory. Thus, Bradyrhizobium strains of each nodulation type unformed a specific cluster. However, types A and B formed one sub-cluster, and types A and C did another cluster. These findings indicated that type B was distantly related to type C in regard to the structure of genomic DNA, while type A located in an intermediate position between type B and type C.