Abstract: Screening a highly efficient phosphate-solubilizing bacteria from the rhizosphere soil of Pinus massoniana is to provide strain resources for artificial planting and microbial fertilizer of P. massoniana seedlings. The plate dilution method and molybdenum antimony resistance colorimetric method were used to isolate and screen phosphate-solubilizing bacteria from the rhizosphere soil of P. massoniana. The strain was identified based on the morphological,physiological and biochemical properties and the analysis of 16S rDNA gene sequence. By measuring the abilities of the strain solubilizing 4 poorly soluble phosphates,a more easily soluble phosphate was screened out,and the solubilizing characteristics of this phosphate by the strain under different conditions were explored. Finally,the effects of the strain on the growth of P. massoniana seedlings were analyzed by measuring the seedling biomass,plant phosphorus content,and available phosphorus content in the rhizosphere soil. A strain of bacterium WJ2 with strong phosphorus-solubilizing capacity was screened from the rhizosphere of P. massoniana. The amount of solubilized phosphorus reached 244.13 mg/L after the strain was cultured in inorganic phosphate liquid medium for 5 d. The strain was identified as Paraburkholderia sp. The highest phosphate solubilizing capacity of the strain in 4 phosphorus source media was Ca₃（PO₄）₂（204.42 mg/L）> AlPO₄（177.70 mg/L）> FePO₄·2H₂O（151.82 mg/L）> CaHPO₄·2H₂O（108.19 mg/L）. Pearson correlation analysis showed that there was a significantly negative correlation between the changes of phosphate solubilizing capacity and pH of WJ2 in these 4 different inorganic phosphorus sources media. The strain WJ2 utilized various carbon sources such as lactose and glucose,and effectively solubilized Ca₃（PO₄）₂ while using urea,ammonium sulfate,ammonium nitrate as nitrogen sources,and it had a high ability of solubilizing phosphate under the conditions of C/N 10∶1,concentration of NaCl 0 g/L,and initial pH 8.0. In the pot experiment,the seedling height,taproot length and fresh weight of P. massoniana seedlings after inoculating the strain WJ2 increased by 11.74%,45.73% and 46.00%,respectively,compared with the control. In addition,the soil available phosphorus and plant phosphorus content of P. massoniana inoculated with the strain WJ2 also increased significantly,the increase amounts were 18.32% and 13.82%,respectively. The strain WJ2 solubilizes a variety of insoluble inorganic phosphates,and presents a significant effect on increasing the effective phosphorus content of the soil and promoting the growth of P. massoniana seedlings. Thus,WJ2 is a promising microbial resource for the production of high-efficiency biological phosphorus fertilizer.

Key words: bacteria, phosphate-solubilizing characteristics, carbon sources, nitrogen sources, C/N, biological phosphorus fertilizer