Screening Of Phosphate-solubilizing Bacteria And Effect Of Promoting Soybean Growth

Phosphorus is the main component of organic compounds in plant.Most of the phosphorus is insoluble in soil,which cannot be absorbed by plants directly.Phosphate solubilizing microorganisms(PSMs)are ubiquitous in soil and could play an important role in phosphorous cycling,converting insoluble phosphate into soluble forms which are available to plants.The minerals also impact the survival and multiply of microbes.Therefore,the study of the interaction of minerals and microbes has become a hotspot of geomicrobiology.In this study,the interaction of Phosphate solubilizing microorganisms and phosphate complex could realize the cycle of phosphorus.Studying the function of microbial activating soil Phosphorus is important for Improving phosphorus uptake efficiency and reducing chemical phosphorus fertilizer inputs.In this study,seven phosphate-solubilizing bacteria strains with stronger p-solubilizing ability from rhizosphere soil of soybean were collected in Nanjing Fujiabian agricultural science Park.Strain were identified according to physiological characteristics observed,biochemical characteristics tested and 16S rRNA sequencing analysis.The strain san5,san8 and DK6 were tentatively identified as Enterobacter sp.,San6 and DLT2 were identified as pantoea sp.,DLT3 and DLT4 were identified as Acinetobacter sp.The ability of producing indole acetic acid(IAA)and siderophore of various strains were detected by qualitative test.Strain san6 and DLT3 was found to be able to produce both IAA and siderophore.Strain SAN5,SAN8 and DK6 were able to produce IAA but not siderophore.Strain DLT4 was able to produce siderophore but not IAA.Different microbes have different P-solubilizing effects.The dissolving Ca3(PO4)2 and fluorapatite abilities of various strains had been studied by flask-shaking test.The results showed that the solubilizing Ca3(PO4)2 and fluorapatite efficiency of strain san8 and DLT4 were higher than the others.The category and quantity of organic acids secreted by variou strains were significant different,and most strains could produce oxalic acid,malic acid,malonic acid,acetic acid.It was found that available P in the culture of the isolate SAN8 reached 589.69mg · L-1 after 6-day incubation on the dissolution of Ca3(PO4)2,while the pH value decreased from 7.20 to 3.59.Available P in the culture of the isolate SAN8 reached 517.93 mg · L-1.The pH value decreased from 7.20 to 3.59.Results from HPLC analysis showed that SAN8 mainly release 1168.42 mg · L-1 oxalic acid,652.67 mg · L-1 malic acid,1438.12 mg · L-1 lactic acid,894 mg · L-1 acetic acid.SAN8 mainly release 647.50 mg · L-1 oxalic acid and 115.70 mg · L-1 propanedioic.It was found that available P in the culture of the isolate SAN8,DLT4 and NJAU-12 reached 102.13 mg · L-1,52.26 mg · L-1 and 204.52 mg · L-1 after 10-day incubation on the dissolution of fluorapatite.The pH value of SAN8 decreased from 7.20 to 3.59 after 2-day incubation.DLT4 decreased from 7.20 to 3.83 after 8-day incubation.NJAU-12 decreased from 7.20 to 2.84 after 8-day incubation.Studies on the interaction bacteria with phosphate complex showed that strains SAN8,DLT4 and NJAU-12 could survive in the surface minerals.During the process of metabolism,the strains colud secret organic acids,siderophores and reduction of pH then interacted with phosphate complex.In pot experiments,When the soil was inoculated with PSB-inclusive organic fertilizers,the height,leaf width,diameter dry weight of soybean and accumulation of phosphorus removal etc had significant difference between CK and the treatments with the addition of PSB strains.The chlorophyll of mix treatment was increased.by 28.03%.But height was disincreased by 12%,Phosphorus accumulation of the four treatments.in soybean increased by SAN8 31.40%,A 30.23%,DLT4+SAN8 17.44%and Mix 34.88.With phosphorus fertilizer applying,the effect on increasing the content of available phosphorus in soil was Mix>SAN8>DLT4+SAN8>A>DLT4>CK.