Genetic diversity among microsymbionts of Lathyrus, Vicia , Oxytropis and Astragalus legume species from Baikal region

Rhizobia are Gram-negative soil microorganisms that form intracellular nitrogen-fixing symbiosis with leguminous plants. Investigations of symbiotic systems with the participation of endemic or relict species have a particular importance for understanding of the evolution of plant-microbe interactions. The purpose of our work was to create a representative collection of microsymbionts of endemic Baikal legumes, as well as to estimate their biodiversity. The study of taxonomic positions of 69 isolates from root nodules Lathyrus humilis, Vicia baicalensis, Astragalus mongholicus and Oxytropis sylvatica was conducted. For primary identification of these isolates the methods of ITS-RFLP analysis was used that divided strains into 33 groups with identical DNA-profile. Then the taxonomy positions of isolates were determined by the 16S rRNA gene ( rrs ) and ITS region sequencing. Phylogenetic analysis revealed the considerable genetic diversity among microsymbionts of plants studied. Rhizobial isolates belonged to 5 genera: Rhizobium (family Rhizobiaceae ), Mesorhizobium and Phyllobacterium (family Phyllobacteriaceae ), Bosea and Tardiphaga (family Bradyrhizobiaceae ). In addition, non-rhizobial isolates belonging to the genera Herbiconiux, Leifsonia, Burkholderia and Stenotrophomonas were obtained. It is known that some species of these genera may be present in the nodules of legumes, but also be inhabitants of rhizosphere or phyllosphere of different plants. The presence of atypical rhizobial microsymbionts in the studied plants was noted, which may indicate the active formation of relationships between partners in the legume-rhizobial systems of Baikal region.