Plant growth promoting microorganisms were isolated and screened from mossy crusts in southern fringe of Gurbantunggut desert, and expatiated their growth promoting characteristics and exploring the growth promoting effect has positive significance for exploring and applying functional microbial preparation, promoting vegetation restoration and enhancing desert sand fixation capacity. Culturable microorganisms were isolated subcutaneously from 0 cm to 20 cm soils under the moss biocrusts with the method of enrichment culture. The microbial strains with the ability of phosphate solubilization, siderophores production and indoleacetic acid (IAA) secretion were screened adopting selective media. Then, strains were re-screened by mo-Sb resistance colorimetry, CAS solution and Salkowski colorimetry, respectively for the content of soluble phosphorus, the concentration of iron producing carrier, and the content of IAA, and classified and characterized the strains with excellent performance. The excellent strains were identified by morphological observation,physiological and biochemical characteristics, molecular biological identification. The result showed that 31 growth-promoting strains were screened out, among these 31 strains, 31 also were able to dissolve phosphorus, 13 also to produce siderophores, 28 also to secrete IAA. Strain LB5WH had the highest capacity of dissolving inorganic phosphorus, with dissolving capacity of phosphorus at 302.24 mg/L; strain LB15 had the highest siderophore-producing ability, with producing iron carrier Su value (Siderophore units) at 85.7%; strain GA20 had the highest activity of IAA secretion, with IAA production at 15.46 mg/L. Strains LB5WH and LB15 had the ability of phosphate-solubilizing, siderophores production, and IAA secretion. Strains GA20 had the ability of dissolving organic phosphorus and secreting IAA. And the ability of the strain to dissolve inorganic phosphorus was stronger than that of the strain to dissolve organic phosphorus, and there was a significant negative correlation between the amount of inorganic phosphorus dissolved by the strain and the pH value of culture medium. The identification results of excellent strains showed that strain LB5WH belonged to genus Bacillus, strain LB15 belonged to Lysinibacillus, and strain GA20 belonged to Stenotrophomonas. These three strains had more growth-promoting functions and had the potentials to develop biological fertilizer. The results of this study provided microbial resources for enriching the resources of growth-promoting microorganisms in arid area, further study on ecological regulation mechanism of soil-microbe-plant interaction under the mossy biological crust and the growth-promoting mechanism of desert plant growth-promoting microorganisms. |