Genetic diversity of rhizobial strains isolated from the relict legumes <em>Gueldenstaedtia monophylla</em> and <em>G. verna</em> growing in the republics of Altai and Buryatia (Russia)

For the first time, bacteria were isolated and identified from the root nodules of relict legumes Gueldenstaedtia monophylla Fisch. and G. verna (Georgi) Boriss. growing in the republics of Altai and Buryatia. The taxonomic position of the 29 obtained isolates was determined by sequencing the 16S rRNA gene (rrs). Showing a significant biodiversity, the isolates from G. monophylla and G. verna belonged to five genera of the order Rhizobiales: Mesorhizobium and Phyllobacterium (family Phyllobacteriaceae), Rhizobium (family Rhizobiaceae), Bosea (family Boseaceae), Bradyrhizobium (family Bradyrhizobiaceae). Three isolates which belonged to the species Bradyrhizobium valentinum and Rhizobium alamii showed 100 % of rrs-similarity with the type strains B. valentinum LmjM3T and R. alamii GBV016T, respectively. Six isolates of the genera Bosea and Rhizobium had a low level of rrs-similarity with the closest type strains (less than 99.5 %), which indicates that they may be assigned to new species. The data obtained can be used to itemise taxonomy within the order Rhizobiales, as well as to reveal the mechanisms of the formation of specific plant-microbial relationships during the evolution of symbiosis by studying the intermediate link between the extinct and modern rhizobia-legume symbiotic systems.