Quantitative distribution and character analysis of Sinorchizobium fredii in Shanxi Province

There is a wide distribution of Sinorchizobium fredii,a stress resistant rhizobium in Shanxi Province.The quantified number of Sinorchizobium fredii is between 5100～5100000/g of soil,about 99.4% of the total indigenous soybean rhizobial population in Shanxi.These rhizobia strains are found to nodulate on local “Jindou” soybean cultivars at a minimum level of 80%,but not at all on western “Osumi” soybean cultivars.Effective strains of S. fredii are observed to have good inoculation and nitrogen fixing capability on local soybean cultivars ‘Jindou 19’ and ‘Jindou 20’.They are also found to have acid production activity and well adapted to the alkaline soils of Shanxi.This character is observed to activate rhizospheric nutrition which may be equally important in the nodulation and fixation activities of the rhizobia strains.