Diverse spp. with Similar Symbiosis Genes Nodulate Peanut in Different Regions of China: Characterization of Symbiovar sv. Arachis.

A total of 219 rhizobial strains isolated from peanut grown in soils from six peanut croplands in Zhengyang county, Henan Province, were typed by PCR-RFLP of IGS sequences. Their phylogenetic relationships were refined on representative strains using sequence analyses of 16S rRNA genes, housekeeping genes (, , ) and symbiosis genes (, and ). The 219 rhizobial isolates were classified into 13 IGS types, and twenty representatives were defined within eight genospecies: covering 5 IGS types (75.2% of total isolates), (2 IGS types, 2.7% total isolates), (1 IGS type, 11.3% total isolates) and five novel genospecies (5 IGS types, 0.9 to 3.2% total isolates). All representative strains had identical , and sequences except for one sequence. With this one exception, these sequences were identical to those of the type strains of species and several genospecies isolated from peanut in different regions of China. The sequences of all strains showed < 67% similarity to the closest strains on the Genbank database indicating that they are representative of a novel symbiovar. This study has shown that (1) diverse spp. with similar symbiosis genes nodulate peanut in different regions of China. (2) Horizontal transfer of genes involved in nodulating peanut is common between species in soils used to grow the crop in China. (3) The strains studied here are representative of a novel symbiovar that nodulates peanut in China. We propose the name sv. arachis for this novel symbiovar indicating that the strains were isolated from . Results here have practical implications in relation to the selection of rhizobial inoculants for peanut in China.