Abstract

We identified 12 strains of root-nodule bacteria isolated from Pueraria mirifica, an indigenous Thai medicinal legume, grown naturally in Thailand. Sequence analysis of the 16S rRNA gene indicated that 9 and 3 strains belonged to the generaRhizobium and Bradyrhizobium, respectively, with high identity (96 - 100%). All 9 P.mirifica-nodulating Rhizobium strains were placed in Rhizobium spp. clade of the constructed phylogenetic tree. While, the closest phylogenetic neighbours of P. mirifica-nodulating Bradyrhizobium were Bradyrhizobium liaoningense,Bradyrhizobium yuanmingense and Bradyrhizobium japonicum. The strains were characterized by phenotypic characteristics including utilization of carbon and nitrogen sources, resistance to antibiotics, requirement for vitamins and enzymatic patterns. Both genera that nodulated P. mirifica were phenotypically indistinguishable. Growth tests at different conditions revealed that the strains, even among the same genus, varied in their response to the levels of temperature, pH and NaCl. Rhizobium DASA 64006 was the only one strain that could propagate at all desired conditions.

Key words: Pueraria mirifica, root-nodule bacteria, symbiont, Rhizobium,Bradyrhizobium, 16S rDNA, enzyme pattern.