Screening,Identification And Mechanism Of Phosphate Solubilizing Fungus In Soybean Rhizosphere

Phosphorus-solubilizing fungi,as an important part of soil phosphorus-solubilizing microorganisms,play an important role in the utilization of potential phosphorus sources in farmland soil and the reduction of chemical fertilizer application.Moreover,the phosphate-solubilizing capacity and stability of phosphorus-solubilizing fungi are higher than other types of strains.In the present study,the soybean rhizosphere soil in the experimental field of Heilongjiang Academy of Agricultural Sciences was used as the research object.The traditional microbial culture method,morphological observation and ITS r DNA sequencing technology were used to screen and identify the phosphate-solubilizing fungi in the soil,and to explore the phosphate-solubilizing ability,phosphate-solubilizing characteristics and phosphate-solubilizing mechanism of the strains.The main results of the experiment are as follows:(1)Three strains of phosphate-solubilizing fungi were isolated and screened from the soil,namely WR1-4,WR1-1 and WR2-8.The identification found that the strains WR1-4 and WR1-1belong to the genus Talaromyces sp.,WR2-8 belongs to Ascomycota sp..(2)Three phosphate-solubilizing fungi have different ability to dissolve insoluble phosphorus sources,and the dissolving ability of calcium phosphate and aluminum phosphate is shown as calcium phosphate > aluminum phosphate.The ability of the three phosphatesolubilizing fungi to dissolve the other three phosphates was significantly different,and the ability of WR1-4 to dissolve phosphates is iron phosphate > aluminium phosphate > phosphate rock.The phosphate solubilization capacity of WR1-1 is iron phosphate > phosphate rock >aluminum phosphate.The ability of WR2-8 to dissolve phosphate is aluminum phosphate >phosphate rock > iron phosphate.(3)The analysis of the phosphate solubilizing characteristics(temperature,initial p H,inoculum,carbon source,nitrogen source)of three phosphate-solubilizing fungi showed that,the optimum culture temperature of WR1-4 and WR2-8 is 28?,and the optimum culture temperature of strain WR1-1 is 35?.The optimal initial p H value of WR1-4,WR1-1,and WR2-8 are all 7.The optimal inoculation amount of WR1-4 is 1%.The optimal inoculation amount of WR1-1 is 10%,and the optimal inoculation amount of WR2-8 is 5%.When strains WR1-4,WR1-1 and WR2-8 are used for phosphorus solubilization,the best carbon source is glucose and the best nitrogen source is ammonium nitrogen.(4)There are eight kinds of organic acids produced by strains WR1-4,WR1-1,and WR2-8by liquid chromatography.The phosphate solubilization process of WR1-4 and WR1-1 is mainly related to the secretion of oxalic acid,and WR2-8 dissolving phosphorus is related to oxalic acid,citric acid and fumaric acid.Ultraviolet spectrophotometry was used to detect the content of phosphatase produced by the three phosphate-dissolving fungi,and the time for alkaline phosphatase and acid phosphatase to reach the maximum was the same.Based on the correlation analysis between organic acid content and available phosphorus content,it is speculated that the three phosphate dissolving fungi mainly dissolve phosphorus through the secretion of organic acids.