Virulence of legume bacteria on soybean and degree of symbiotic nitrogen accumulation in soils of Amur river region

Indicators of soybean nodules development in meadow-flood-plain soils of Amur River region were analyzed. Virulence of local strains and a share of symbiotic nitrogen accumulation by the cultivars Harmony and Nega 1 were determined. There were used a method of comparison to non-legume crop (oat) and a method of comparison of an parental cultivar to its mutant form which develops insignificant quantity of nodules with low activity. The local soybean rizhobia in studied soils are characterized with a high virulence (from 45 to 100%) to soybean cultivars of the different geographical origin. For strains of Bradyrhizobium japonicum (slow-growing forms) the virulence limits for studied cultivars are from 73 to 100% and for strains of Sinorhisobium fredii (quick-growing forms) - 40-100%. A share of symbiotic nitrogen accumulation by the cultivars Harmony and Nega 1 in studied conditions was differed insignificantly and was in the various vegetative periods 63-82%. The both methods of determination of a share of symbiotic nitrogen accumulation showed the high similarity: from 63-67 to 82-82%.