Measurement of Nitrogen Fixation Capability and Excreted IAA Capability of PGPB Isolated from Cotton Rhizosphere in Salina

In this study 182 associative nitrogen fixation strains are isolated from the cotton rhizosphere at Aral City,Xinjiang by applying the gas chromatograph and acetylene reduction method,in which 104 strains are isolated from the long stapled cotton rhizosphere,and the nitrogen fixation capability and the capability of excreting growth hormone are measured.At last 8 strains with high nitrogenase activity are selected to analyze and research,in which the nitrogenase activity of AC2 strain is the highest and for 636.61 nmoL C2H4/(h·mL),and reaches an extremely significant level.But the value of NC1 strain is the lowest and for 23.40 nmoL C2H4/(h·mL) only.The difference between the highest and lowest values of nitrogenase activity of the strains isolated from upland cotton rhizosphere is as high as 27 times,and it is higher than that isolated from long stapled cotton rhizosphere.If nitrogenase activity is considered only,the fine strains with exploiting potential in the upland cotton fields,such as AC2,are more.The nitrogen fixation capability of nitrogenase in the long stapled cotton rhizosphere is relatively poor.All strains isolated from both upland cotton rhizosphere and long stapled cotton rhizosphere have the capability of excreting growth hormone.NL2 and NL1 strains are better than others at the aspects of nitrogen fixation capability and capability of excreting growth hormone.