Characterization of bradyrhizobia associated with soybean plants grown in Ukraine

Abstract

The phenotypic and genotypic features of soybean nodule bacteria with different growth rates common in soils of Ukraine have been studied. The obtained results suggest high heterogeneity of soybean microsymbionts. It has been established that all studied strains are able to form active symbiotic relationships with soybean. When interacting with Chinese cowpea, intensive-growing strains form an ineffective symbiosis with a low nitrogen fixation level (phenotype Nod+Fix-), while slow-growing strains form complete nitrogen fixing systems (phenotype Nod+Fix+). Upon cultivation in the mannitol yeast medium, intensive-growing strain B. japonicum KC19 produces a significant amount of auxins and cytokinins, while the slow-growing strain B. japonicum KC23 is significantly superior by the amount of gibberellins. According to the organization of the genome defined in REP-PCR, studied strains of soybean rhizobia belong to two genetic groups, which corresponds to the division of strains into groups by the growth rate (slow-and intensive-growing). Based on the RFLP analysis of rpoB gene, using restriction enzymes MspI, HaeIII and NdeII, intensive-growing strains were combined into one rpoB type, while slow-growing strains belong to 2-3 rpoB types.