Soluble Phosphorus Effect Of Phosphate Solubilizing Bacteria From Rice Rhizosphere And Its Promoting Effect On Plant Growth

Phosphorus is one of the necessary nutrients for crops, which plays a key role in crop metabolism. Soil phosphorus solubilizing microorganisms make the soil of poorly soluble or insoluble phosphorus converted into the easily absorbed and used phosphorus by plants, which can significantly improve the soil phosphorus content, and reduce soil adsorption of phosphate fixation, it is recognized as safe, economical, efficient activation of biological measures soil insoluble phosphorous. In this experiment, the phosphate dissolving bacteria with strong dissolved Ca3(PO4)2 were isolated and screened from the rhizosphere soil of rice, and a series of studies were carried out, the main results were as follows:1. Two inorganic phosphate dissolving bacteria were screened out by NBRIP culture medium, which were named as NDW1 and NDW3. By 16 S rDNA sequence analysis of two isolates identified NDW1 as Enterobacter and NDW3 as Serratia, and they all has a natural resistance to ampicillin.2. Through single factor and orthogonal test, the optimum conditions of phosphate dissolving bacteria were optimized under the conditions of different carbon source, nitrogen source and pH value, results show: Strains of phosphate solubilizing capacity and growth rate have no obvious correlation; L9(3)4 orthogonal test showed that two strains of the optimal combination of glucose, peptone and PH = 6, primary and secondary order of C source>pH value>N source. Based on the optimized culture medium, the phosphate dissolving ability of two strains to four kinds of insoluble phosphate was determined, the results showed the presence of dissolved phosphorus ability Ca3(PO4)2> FePO4> AlPO4> soy lecithin phenomenon.3. The phosphatase, GDH and GADH activities of the strains were determined based on the optimized medium, results showed phosphatase, GDH and GADH activity increases firstly and then decreases as the time change, strains dissolved phosphorus content was basically maintained in the higher range when phosphatase enzyme living up to the maximum, but strains dissolved phosphorus content is not within the upper range when GDH and GADH activity are maximum.4. GADH small subunit gene ga2 dh was cloned from Serratia NDW3, the sequence size is 781 bp, its consistency is 99.62% with GenBank Serratia sp. SCBI(CP003424.1). By qPCR analysis, expression quantity of small subunit gene expression ga2 dh decrease gradually as time increased with 48 h. The ga2 dh small subunit gene was connected with expression vector pET-28 a, and the recombinant plasmids were transformed into E. coli BL21 to induce expression, protein expression by SDS-PAGE electrophoresis analysis showed that the molecular size of approximately 27 kD.5. The two phosphorus solubilizing bacteria have produced indole acetic acid(IAA) ability, and sand culture and soil culture pot experiment were carried out, the results showed that plant height, root length, maximum leaf length, wet ground heavy, underground wet weight, shoot dry weight, underground dry weight, chlorophyll content, plant total phosphorus and available phosphorus of rice by broth treatment were significantly higher than those inoculated control group, showing that the two strains can promote the growth of rice seedlings significantly, and has a good effect on phosphorus dissolving.