Genetic diversity of microsymbionts from legumes Oxytropis putoranica M. Ivanova, Oxytropis mertensiana Turcz., Astragalus norvegicus Grauer, Astragalus tugarinovii Basil. growing on the Putorana Plateau in Arctic Russia

There is a significant potential for the introduction of legumes into the Arctic regions of Russia. The ability of legumes to form a nitrogen-fixing symbiosis with nodule bacteria is one of their most important characteristics. The article studies the genetic diversity of the 24 bacterial strains isolated from root nodules from wild populations of legumes Oxytropis putoranica M. Ivanova, O. mertensiana Turcz., Astragalus norvegicus Grauer, and A. tugarinovii Basil. collected on the Putorana Plateau (Krasnoyarsk region, Arctic Russia). The microbial strains were isolated using yeast broth made with a standard method using YMA mannitol. Genomic DNA was isolated from pure cultures and the primary identification of the strains was carried out by PCR followed by sequencing of the 16S rRNA marker gene fragment. To clarify the identity of the species, ITS sequencing of the region was performed. The isolates were assigned to six genera and to five families of the order Hyphomicrobiales: Pararhizobium and Neorhizobium (family Rhizobiaceae), Phyllobacterium (Phyllobacteraceae), Microvirga (Methylobacteriaceae), Bosea (Boseaceae) and Tardiphaga (Bradyrhizobiaceae). Isolates from O. putoranica nodules were identified as Neorhizobium galegae, Bosea sp., Bosea vaviloviae, and Tardiphaga robiniae. The isolated nodules of O. mertensiana were identified as Pararhizobium herbae, Tardiphaga robiniae, Microvirga ossetica, and Microvirga sp. Microsymbionts of A. norvegicus were assigned to Bosea psychrotolerans and to Pararhizobium herbae and Tardiphaga robiniae species, while isolates from A. tugarinovii were identified as Phyllobacterium zundukense, Bosea sp., and Tardiphaga robiniae. Symbiotic the nodA gene was detected in strains P. herbae P14/2-4 and P20/1-1, P. zundukense P17/1-7 and P17/3-2, while the nodC gene was not detected in any of the strains. The sterile test tube experiment confirmed the inability of strains P. herbae P14/2-4 and P20/1-1 to form nodules in host plants O. mertensiana and A. norvegicus, as well as in other wild arctic (A. tugarinovii, O. putoranica) and forage legumes (Trifolium repens, Vicia cracca, and Lathyrus pratensis). The results obtained expand the understanding of the taxonomic status and biodiversity of local microsymbionts of wild legumes that grow on the Putorana Plateau. The study of the symbiotic efficiency of Arctic rhizobia will allow us to identify the most promising strains for the development of effective biofertilizers for the cultivation of forage and pasture legumes under the extreme soil and climatic conditions of the Russian Arctic. In turn, the creation of highly adapted legume-rhizobial systems based on valuable genetic resources of Arctic rhizobia strains will expand the range of legume species promising for use in the creation of multi-component agrophytocenoses necessary for the sustainable development of animal husbandry in Arctic regions of Russia.