Currently, it is known that 16S rRNA gene analysis is not the most reliable method to differentiate
close species of Rhizobium and Bradyrhizobium, but this gene is the most suitable to classify new strains of rhizobia because it constitutes the basis of rhizobial classification (Kuykendall, 2005). The 16S rRNA gene sequence results of our study showed that M. pinnata is a promiscuous legume, Romidepsin order able to establish efficient symbiosis with Bradyrhizobium and Rhizobium. It was found that fast-growing Rhizobium spp. were the predominant microsymbionts with M. pinnata from the soils collected from Akola, Bijapur, Hanumanjunction, Choppadandi and Chintapalli, and Bradyrhizobium elkanii from the soils of Adimilli and Penpahad, whereas Bradyrhizobium spp. were the predominant microsymbionts
found with M. pinnata from rest of the soils. Variations in the nature of rhizobia nodulating the M. pinnata in different geographic and climatic areas so far have not been reported, but it has been reported in several acacia species (Lafay & Burdon, 2001; Liu et al., 2005; Gu et al., 2007; Lafay & Burdon, 2007; Bala et al., 2003), Parasponia andersonii (Trinick et al., 1989), Pachyrhizus erosus (Fuentes et al., 2002), Prosopis glandulosa (Jenkins, 2003), Acacia mangium (Ngom et al., 2004), and Pueraria mirifica (Neelawan et al., 2010). This symbiotic promiscuity, Bay 11-7085 found mostly in legumes from warm or tropical parts of the world, ensures effective nodulation of host plant in most soils, thereby increasing this website its ability to succeed in colonizing barren sites and to spread into new habitats. To conclude, the present study is the first report that phenotypically and genotypically characterizes root-nodule microsymbionts of the multipurpose tree legume, M. pinnata. The microsymbionts were identified genotypically as Rhizobium and Bradyrhizobium, predominant symbionts with most legume species. These genera are genotypically and phenotypically distinct from each other based on
the constructed phylogenetic trees. Additional experimental work would be necessary, for instance DNA–DNA hybridization, multilocus sequence analysis of housekeeping genes, and phylogenetic reconstructions based on accessory symbiotic loci such as nodB, nodC, or nifH. This study therefore provides the basis for further research on the phylogeny and biodiversity of rhizobial strains nodulating M. pinnata, as well as their use as inoculants to improve growth and nitrogen fixation in arid and semi-arid lands of India and other countries. Physiological and biochemical studies are the basis for detailed polyphasic taxonomy and should not be used alone in taxonomic analysis. This was well illustrated by the differences between clusters defined here using phenotypic characteristics and molecular tools.