| Phosphorus is one of the main nutrients in plant growth and development.Phosphorus in soil exists mainly in two forms of mineral phosphorus and organic phosphorus, its lower bioavailability of phosphorus is not easily be absorbed by plants.There are a lot of soil microorganism having the ability to dissolve phosphorus,including actinomycetes, fungi and bacteria. These phosphorus solubilizing microorganism can digest difficult soluble or insoluble phosphorus in the soil into soluble phosphorus which can be absorbed by plants, and can also secrete plant growth promoting substances which can improve plant rhizosphere nutrition and enhance disease resistance of crops. Therefore, application of efficient phosphorus solubilizing strains screened from rhizosphere soils to activate the insoluble phosphorus in the soil has become the research focus of improving soil phosphorus utilization.In this experiment, the rhizosphere soil of the main maize producing areas in Jilin Province was used as test material. Actinomycetes with phosphate dissolving ability were preliminarily isolated by solid plate culture and selective medium culture.Then, efficient phosphate dissolving strains were screened by comparison of available phosphorus content in fermentation broth. The basic characteristics, phosphate solubilizing ability and characteristics of the three isolated phosphate solubilizing strains were investigated for providing excellent strains for the development of highly efficient microbial fertilizers. The results are as follows:1. Three efficient phosphorus solubilizing actinomycetes were isolated from the soil samples, and were named as 47, S14, SY12, respectively.2. The identification results of colony morphology, physiological and biochemical characteristics and 16 SrDNA sequence showed that the three strains belong to the genus Streptomyces sp.3. The phosphorus dissolving dynamics, effects of different carbon, nitrogen,phosphorus source, temperature and other conditions on the ability of phosphate solubilization and and the relationship between the amount of dissolved phosphorus and pH in different culture time of the three phosphorus solubilizing actinomycetes were investigated. These results are as follows:The phosphate solubilization ability of the strains was affected by the culture conditions such as carbon source, nitrogen source, phosphorus source, temperature.Dynamic analysis of phosphorus solubilizing capacity showed that the ability of dissolving phosphorus of the strains was the best when sucrose and glucose were used as carbon source, the ability of dissolving phosphorus the strain 47 was the best when ammonium sulfate used as nitrogensource, while that of the S14 and SY12 was the best when potassium nitrate were used as nitrogen source. Temperature dynamic analysis showed that the optimum culture temperature of the strain 47 is 38 ℃, that of the strain S14 is 48℃, and that of the strain SY12 is 28 ℃. Phosphorus dissolving dynamic analysis of five different insoluble phosphate showed that the three strains has different phosphorus sobilizing capacity, the strain 47: Lecithin> AlPO4> FePO4>Ca3(PO4)2> PRs; Strain S14: Lecithin> AlPO4> PRs> Ca3(PO4)2> FePO4; strain SY12: Lecithin> Al PO4> PRs> Ca3(PO4)2> FePO4. With culture at different times, the amount of dissolved phosphorus and pH showed some correlation. The amount of soluble phosphorus and pH showed a certain correlation with different incubation time.4. The results of high performance liquid chromatography(HPLC) analysis showed that three phosphorus solubilizing actinomycetes secreted organic acids of oxalic acid, malic acid, acetic acid, citric acid, succinic acid, lactic acid in the process of phosphate dissolution, and the type and concentration of organic acids and the amount of dissolved phosphorus has a certain correlation.5. The results of the disease resistance and growth promoting effect showed that the three actinomycetes have inhibitory effect on 9 kinds of pathogenic fungi and 3kinds of pathogenic bacteria, and the three actinomycetes do produce siderophores and indole acetic acid(IAA). |
