Effects Of Saline-alkali-tolerant Phosphate-solubilizing Bacteria On Growth And Rhizosphere Microecology Of Soybean

In recent years,the problem of soil salinization has become more and more serious.Salinealkali soil has fewer nutrients and often shows a state of phosphorus deficiency.Phosphorus is the second major limiting element for crop growth,and low phosphorus content in the soil will limit crop growth.Phosphate-solubilizing bacteria(PSB)will convert insoluble phosphorus into phosphorus that will be absorbed and used by crops.Saline-alkali-tolerant PSB have phosphatesolubilizing ability and it can survive in saline-alkali soil.Saline-alkali-tolerant phosphatesolubilizing bacteria is of great significance for promoting crop growth,reducing fertilizer application and rational development and utilization of saline-alkali land.In this study,four saline-alkali-tolerant PSB were isolated from alfalfa rhizosphere soil growing in saline-alkali soil in Daqing High-tech Zone.The saline-alkali-tolerant PSB were applied to saline-alkali soil,and soybean biomass,physiological index,lipid metabolism and other indicators were measured by pot experiment to clarify the phosphate-solubilizing and growth-promoting function of PSB,and the microecology of soybean rhizosphere soil was analyzed.The results of the study are as following:(1)We measured the physical and chemical properties of alfalfa rhizosphere and bulk soil that grew well on saline-alkali soil,and measured the utilization rate of soil microorganisms on two kinds of soil.The AWCD value(Average Well Color Development)and physicochemical properties of rhizosphere soil were higher than bulk soil,and p H was lower than bulk soil.A total of 98 strains with different morphology were screened in the rhizosphere of alfalfa,and 4 strains with good phosphorus solubilizing effect were selected qualitatively and quantitatively.W5 was identified as Bacillus siamensis,Y7 as Pseudomonas sp.,Y14 as Bacillus wiedmannii,and Y31 as Acinetobacter sp.All the four strains were saline-alkali resistant and could produce phosphatase and phytase,among which alkaline phosphatase produced the highest amount.pho D gene was found in all four strains,and app A gene was found in Y14 and Y31.(2)Four PSB strains had good effects on soybean growth promotion by solubilizing phosphorus in mixing saline and sandy soil and pure mild saline soil.After the application of PSB,soybean could grow normally in phosphorus deficient soil and mild saline-alkali soil.Compared with the control,soybean biomass,chlorophyll and osmotic material contents were significantly increased.The activities of antioxidant enzymes and the content of malondialdehyde showed a downward trend.In addition,the root activity,phosphorus and potassium contents of soybean plants were significantly increased in pure saline-alkali soil.The content of superoxide anion radical in plant leaves and roots was decreased.(3)Lipid metabolism of soybean leaves in Y7 treatment group,which had the best growth promotion effect in pure mild saline soil,was analyzed,and 429 lipids were detected,of which85 were up-regulated and 51 were down-regulated.The differential metabolites were screened,and 30 significantly different metabolites(16 up-regulated and 14 down-regulated)were obtained.The most different metabolic pathway from lipid metabolism was glyceride metabolism,in which glycerol phospholipids increased and glycerol esters decreased.(4)Activities of soil enzyme(Urease,Phosphatase,Sucrase,Cellulase,Catalase)and available phosphorus and potassium contents were significantly increased after the application of PSB.The results of Biolog-Eco experiment showed that the utilization rates of six carbon sources by soil microorganisms showed an upward trend after the application of PSB.After the application of PSB,sequencing of rhizosphere soil results showed that Proteobacteria and Acidobacteria were the main bacterial phyla in the soil.Ascomycota and Teratospora were the main fungal phyla.Compared with the control group,the application of PSB significantly increased the diversity and abundance of soil bacterial and fungal communities,and increased the abundance of beneficial bacteria.In this study,the soybean pot experiment proved that all the four strains had good phosphorus solubilizing and growth promoting function,among which the Y7 strain had the best effect,which promoted soybean growth in saline-alkali soil,improved soybean rhizosphere soil microecology,and enhanced soybean tolerance to saline-alkali soil.