Characterization and De Novo Genome Assembly for New Rhizobium Ruizarguesonis Rhizobial Strain Vst36-3 Involved in Symbiosis with Pisum and Vicia Plants.

Pea and vetch are the important legume crops used as food, forage, and green manure in agriculture. Several new rhizobial isolates were obtained from vetch Vicia sativa root nodules. For one of them, Vst36-3, the nodulation test showed various specificity in relation to plant hosts from the Fabeae tribe, such as pea and vetch. It is in contrast to typical strains of the Rhizobium leguminosarum species complex (Rlc), which formed effective nodules as in pea and vetch. Here, whole genome sequencing was performed followed by de novo genome assembly for Vst36-3 strain. As a result of de novo genome assembly, seven contigs were generated using Oxford Nanopore Technology long reads and subsequently Illumina short reads. Phylogenetic analysis allowed us to identify this strain as Rhizobium ruizarguesonis Vst36-3. Analysis of the Sym plasmid containing the nod and nif genes revealed that R. ruizarguesonis Vst36-3 has a complete suite of essential genes for the development of symbiosis. Nevertheless, this new strain forms ineffective nodules in pea. This makes Rhizobium ruizarguesonis Vst36-3 attractive for the search and investigation of new factors of host specificity in future.