Abstract: This study aims to acquire the saline-tolerant root-promoting rhizobacteria（PGPR）with multi-function of fixing nitrogen,dissolving phosphorus and synthesizing the IAA for increasing the peanut yield in saline soil. Spread plate was used to isolate the peanut rhizosphere nitrogen-fixing bacteria in saline soil,16S rDNA was to identify the sequence,and acetylene reduction method to determine the nitrogenase activity. Total 22 nitrogen-fixing strains were obtained,and their nitrogenase activities were between 125.82-346.32 nmol C₂H₄/（h·mL）. All strains had the activities of ACC deaminase and dissolving insoluble phosphorus source;their ACC deaminase activity were among 0.12-1.26 U/mg,the amount of dissolving tricalcium phosphate was between 1.45-53.58 mg/L,the that of dissolving ferric phosphate was between 1.45-8.27 mg/L,and that of dissolving aluminum phosphate was between 1.1-22.82 mg/L. Ten strains of them secreted IAA with the amount ranging in 1.36-1.36 g/mL,accounting for the 55% of the total strains. The ten strains were also tested for their survival abilities in different concentrations of NaCl and pH,results showed that the maximum tolerance to pH was 9 and the maximum tolerance to NaCl was 1.5 mol/L. In conclusion,the 10 strains demonstrate strong tolerance to salinity and showed their potential of applying in saline soil.

Key words: saline soil, nitrogenase activity, P-releasing, ACC deaminase, IAA, tolerance to salinity