GENETIC DIVERSITY AMONG MICROSYMBIONTS OF Lathyrus, Vicia, Oxytropis AND Astragalus LEGUME SPECIES FROM BAIKAL REGION

Abstract

A b s t r a c t 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 plantmicrobe 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 DNAprofile. 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 legumerhizobial systems of Baikal region.Keywords: legumes of Baikal region, taxonomy of rhizobia, ribosomal genes sequencing.Nodule bacteria (Rhizobia) belong to a large genetically diverse group of Gram-negative soil microorganisms that form intracellular nitrogen-fixing symbiosis with legumes. One of the urgent tasks of modern biotechnology is the study of mechanisms of interaction of legumes with rhizobia, required for evidence-based selection of highly effective plant-microbe systems [1].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. These unique objects include Baikal legumes, such as low-growing vetchling (Lathyrus humilis), a Late Pleistocene relict of the South Siberian-Severouralsk area [2]; Mongolian milk vetch (Astragalus mongholicus), a rare medicinal plant [3,4]; Baikal endemics Baikal pea (Vicia baicalensis) and forest oxytrope (Oxytropis sylvatica) [5].Few data on Astragalus microsymbionts show a great diversity of these microorganisms belonging to different genera of order Rhizobiales: Rhizobium, Sinorhizobium, Bradyrhizobium,. Vetch-