Isolation Of Soil Phosphate Solubilizing Bacteria From Changji City,Xinjiang And Effect On Phosphorus Solubilization In Horticultural Plants

The circulation of soil phosphorus is mainly caused by the circulation of microorganisms,plants and soil.The types of phosphorus-dissolving microorganisms and the activities of phosphate-dissolving determine the growth of plants in the soil.In this experiment,soil samples were collected from Changji City,Xinjiang Province,and 30 strains of phosphate-dissolving bacteria were isolated and purified.Six of them were found to have good phosphate-dissolving ability by plate test,and then one strain of high-efficiency phosphate-dissolving bacteria B5 was selected by shake flask culture.The genetic characteristics and various biochemical identifications were carried out,and then the mechanism of dissolving inorganic phosphorus was explored and studied.Finally,the bacteria were applied to the pot experiment to detect the changes of various growth indexes of the plants after the application of the bacterial liquid.The experiment showed that the high-efficiency phosphate-dissolving bacteria were isolated and identified by using calcium phosphate as the only phosphorus source.The effective phosphorus content was 519.66 mg/L after shake flask test.After genetic characterization,strain B5 was identified as a bacterium of the genus Pseudomonadaceae.The phosphate-dissolving ability of the phosphate-dissolving microorganism was not only related to its own nature,but also related to its growth environment.The bacterium was in a wide temperature range.It can dissolve considerable inorganic phosphorus,and it has strong adaptability in areas with large temperature difference between day and night in Xinjiang.p H and salt concentration have a great influence on the phosphorus-dissolving ability of B5.The effective phosphorus content is highest at specific p H and salt concentrations.The phosphate-dissolving ability of the strain is closely related to carbon,nitrogen and phosphorus in the culture system.When calcium phosphate is used as the phosphorus source,the highest phosphorus content is available,followed by calcium phytate,the phosphate dissolving ability of iron phosphate and aluminum phosphate is weak,and the dissolution oforganophosphorus lecithin is less.The effective phosphorus content is 24.85 mg/L..The difference in the composition of the carbon source and the nitrogen source affects the phosphate-dissolving ability of strain B5.The order of phosphorus-dissolving ability of strains under different carbon sources was: glucose>galactose>lactose>sucrose>soluble starch.The order of phosphorus-dissolving ability under different nitrogen sources was(NH4)2SO4>NH4Cl>Urea>KNO3.Most studies have found that the mechanism of phosphate solubilization of phosphate-dissolving bacteria is mainly the mechanism of acid hydrolysis.It is found by GC-MS that B5 produces the following five organic acids,oxalic acid and succinic acid,in the process of dissolving inorganic phosphorus.Glutaric acid,gluconic acid and arabinic acid.When Ca3(PO4)2,Fe PO4,Al PO4 and phytate were used as phosphorus sources,the types and contents of organic acids produced by the strains were different.When calcium phosphate was used as the phosphorus source,the total relative content of organic acids was higher,followed by planting.The content of organic acid secreted by calcium acid,aluminum phosphate and iron phosphate is low.Experiments have shown that the total content of organic acid has a proportional relationship with the phosphate-dissolving ability of the strain.The promoting effect of the strain on the plant does not only dissolve the poorly soluble phosphorus for plant absorption,but also the plant secretes plant growth related hormones,thereby promoting plant growth.Experiments showed that strain B5 produced gibberellin,siderophore and indole acetic acid to promote plant growth.The contents of gibberellin and indole acetic acid were 29.9 mg/L and 4.14 g/L,respectively,and the siderophore activity was19%.In order to further explore the phosphorus-dissolving ability of the high-efficiency phosphate-dissolving bacteria B5,the bacteria were subjected to a pot experiment,and the plants were selected from marigold,tomato and cucumber.The results of pot experiment showed that strain B5 promoted the growth of three kinds of plants,and tomato and cucumber were more obvious than marigold.