[Screening and phosphate-solubilizing characteristics of phosphate-solubilizing actinomycetes in rhizosphere of tree peony.]

A strain PSPSA1 with strong phosphate-solubilizing ability was isolated from the rhi-zosphere of tree peony. This strain was identified based on morphological characteristics, physiological and biochemical experiments, and 16S rDNA sequence analysis. Furthermore, its genetic stabi-lity and phosphate-solubilizing characteristics were investigated. Strain PSPSA1 was identified as the actinomycete Streptomyces albireticuli and showed high genetic stability. The order of phosphate solubilization capacity (PSC) in different phosphorus-source culture media was calcium phosphate (158.5 mg·L-1) > aluminum phosphate (139.9 mg·L-1) > ferric phosphate (127.7 mg·L-1) > lecithin (45.6 mg·L-1). The PSC and pH were significantly negatively correlated in inorganic phosphorus solution, but were not correlated in organic phosphorus solution. When using different carbon sources, PSC was in the order of lactose > glucose > maltose > fructose > sucrose > starch > cellulose. For different nitrogen sources, PSC was in the order of peptone > ammonium nitrate > ammonium sulfate > potassium nitrate > urea. Using glucose as a carbon source and peptone as a nitrogen source, strain PSPSA1 achieved the highest PSC of 202.6 mg·L-1. After incubated for 60 days, the available phosphorus content in soil with a single application of strain PSPSA1 increased by 68.2% compared with control, and the available phosphorus content in soil with mixed application of strain PSPSA1 and organic fertilizer increased by 76.7% compared with a single application of organic fertilizer. The results indicated that the strain PSPSA1 had a strong ability to dissolve insoluble phosphorus and its mixed application with organic fertilizer improved the phosphorus solubilization. Thus, PSPSA1 is a promising microbial resource for the production of high-efficiency biological phosphorus fertilizer.