Genetic Diversity and Metabolites Production of Root-Nodule Bacteria Isolated from Medicinal Legumes Indigofera tinctoria, Pueraria mirifica and Derris elliptica Benth. Grown in Different Geographic Origins Across Thailand

A total of 215 root-nodule bacteria were isolated from 3 medicinal legumes including Indigofera tinctoria, Pueraria mirifica and Derris elliptica Benth. naturally grown in 16 provinces of Thailand. The isolates were evaluated for DNA polymorphism using randomly amplified polymorphic DNA (RAPD) analysis. Isolates generated 92 identical RAPD profiles, indicating highly significant genetic diversity among isolates from distinct geographic areas. The genetic diversity among root-nodule bacteria was affected slightly by the host plants rather than the geographic origins. The total 56 representative strains were characterized by small plasmid and megaplasmid profiles as well as production of acyl homoserine lactone (AHLs)-like quorum sensing molecules, indole-3-acetic acid (IAA) and melanin. Three Rhizobium-like strains nodulating P. mirifica and D. elliptica Benth. harbor the same profile with 2 small plasmids. One Sinorhizobium-like strain and 4 Rhizobium-like strains nodulating I. tinctoria and D. elliptica Benth. harbor the same profile with 4 megaplasmids. The strains varied in their ability to produce AHLs-like molecules and IAA. Melanin production was observed in the only one of Pseudoalteromonas-like strain.