Phylogenetic Comparison of Symbiotic ( NodC and NifH ) and 16S rRNA Genes in Strains of Rhizobium, Mesorhizobium and Bradyrhizobium Isolated from Astragalus, Oxytropis and Onobrychis Spp.

Various studies reported different conclusions on the phylogenetic relationship between symbiotic (nod and nif) and chromosomal (16S rRNA) genes in rhizobia (Haukka et al, 1998). Some studies suggested that the phylogeny of nod genes could be related with the host plant (Ueda et al., 1995). In a previous study, rhizobia (44 isolates) from Astragalus, Oxytropis and Onobrychis pp have been classified into 14 distinct 16S rRNA gene types independently of their host plant and geographic origin. The majority of isolates were classified within the genus Mesorhizobium, and few within Rhizobium and Bradyrhizobium genera (Laguerre et al., 1997). The aim of the present study was to determine the diversity and phylogeny of symbiotic genes (nodC and nifH) of these rhizobia, to compare the distribution of nodC and nifH types to that of 16S rDNA types, and to evaluate the relation between host nodulation range and phylogeny.