Isolation, Identification Of High-Effective Phosphate-Solubilizing Strains And Their Effects On Insoluble Phosphate Solubilization

Phosphate solubilizing microorganisms were isolated in soils from Jiangsu, Hunan, Chongqing, and Yunnan. The isolated strains were identified, and more researches were carried out on phosphate solubilizing ability in vitro and in vitro to develop excellent phosphate solubilizing strains for bettering phosphorus utilization. Main Conclusion is as following:Seven of them, P21,P31,P32,P36,P40,P41,P47, were proved to solubilize phosphate and rock phosphate with high efficiency in plate and broth assay. According to their biophysical and biochemical characteristics and 16S rDNA sequence analysis, strain P31 is identified as Enterobacter agglomerans, P47 is Pantoea agglomerans, P21 is Erwinia herbicola var. ananas, P40 is Citrobacter freudii, P41 is Salmonella choleraesuis subsp. Salamae, and P32 is Stenotrophomonas sp..In broth assay, P31 and P47 can solubilize all the tested insoluble phosphates in medium at different rates, but the other five strains were effective only in some medium.Stain P31 has high effective for Feidong rock phosphate, Lianyungang rock phosphate and Jinning rock phosphate, and P36 is better for Kaiyang rock phosphate and Liuyang rock phosphate. All of them can strongly solubilize Ca₃(PO₄)₂ and Hydroxyapatite with exception of strain P41, which can only solubilize Zn₃(PO₄)₂. In a summary, the seven strains have P-solubilizing specificity for various insoluble phosphates and rocks.During experiment, phosphate-solubilizing ability of strain P21 and P31 were affected by carbon source, nitrogen source, and cultivation time in liquid medium. More available phosphorus was released from Ca₃(PO₄)₂ along with time going by strain P21 and P31 in liquid medium with Kunyang rock phosphate. The best nitrogen source is carbamide for P21 and (NH₄)₂SO₄, for P31,and the best carbon source come from glucose for strain P21, P31, Fructose is not suitable for strain P21, P31 as carbon sources.Strains P21, P31, P47 could tranform insoluble phosphate into available phosphorus both in sterilized and unsterilized soil. But in unsterilized soil, the phosphate solubilizing effect after inoculation of strain is better than in sterilized soil. When Kaiyang and Jinping were applied, the available phosphate content in soil were increased through inoculation with P21, P31, P47. But the available phosphorus content in soil is low if Jinning rock phosphate was applied. The result showed that phosphorus-solubilizing strains exhibited speficity for diffrent kinds of rock phosphate. Inoculation of phosphorus-solubilizing strains can promote crops growth greatly.