The Isolation And Screening Of Saline-tolerant Bacteria And Its Effect On Improvement Of Saline-alkali Soil

With the rapid growth of the global population and the acceleration of urbanization,the amount of arable land per person will decrease.By 2050,50% of arable land will be affected by salt,salinity is one of the most important abiotic factors affecting crop yields.In order to meet the growing dietary needs of people,it has become a top priority to exploit medium and mild saline land into arable land.Currently,microbial remediation method is a method that costs less money and manpower,meanwhile is sustainable.In this paper,saline-tolerant microorganisms were screened,the effects of saline-tolerant microorganisms on plants were investigated and saline-tolerant microorganisms were used to restore saline-alkali land.The main research contents and conclusions were as follows:51 salt-tolerant strains were screened from the high salt environment such as saline-alkali land,after re-screening through the ability to produce extracellular polymeric substance(EPS),31 EPS-producing salt-tolerant bacteria were obtained.The abilities of alkalinity reduction,indole-3-acetic acid(IAA)production,siderophore production and extracellular enzyme production of the re-screened strains were verified.Finally,three saline-alkali resistant microorganisms with excellent performance were obtained,namely Idiomarina sp.YJY02,Halomonas aquamarina DB01 and Bacillus licheniformis JJ2,and the ability to antagonize pathogens of soil-borne diseases was verified.The isolates had the ability to inhibit the growth of Fusarium oxysporum f.sp.,Alternaria solani,Phytophthora sojae and Rhizoctonia cerealis.By using different concentrations of sodium chloride solution to create different salt stress,the effects of screened strains on the growth of wheat seedlings under salt stress were investigated.According to the plate test,all of three strains could increase the germination rate and simplified vitality index of wheat under salt stress.At lower salt stress,the increment of Bacillus licheniformis JJ2 was the largest,andat higher salt stress,the increment of Idiomarina sp.YJY02 was the largest.The strains were used in pot experiments to verify the effect of the strains on the growth of wheat seedlings and colonization of salt-tolerant microorganisms in soil.Results showed that all of three strains can increase wheat seedling shoot length,root length,shoot weight,root weight,antioxidant enzymes and proline content,meanwhile reduce the malondialdehyde content.Idiomarina sp.YJY02 and Halomonas aquamarina DB01 colonize the rhizosphere soil and act directly on the rhizosphere of plants,Bacillus licheniformis JJ2 may promote plant growth by increasing the abundance of functional microorganisms in non-rhizosphere soils,such as Rhizobiaceae and Sphingomonas.The effects of salt-tolerant microorganisms on field crops were also investigated,and the results showed that the isloates increased the height of wheat,the average grain of ear,the biomass of plants and the 1000-grain weight by 7.5%,12.3%,7.7% and 5.8%.The total soluble salt and electrical conductivity decreased by 33.5% and 35.7%,while the total phosphorus,total potassium,available phosphorus and available potassium increased by 13.0%,8.5%,121.6% and 23.3%,respectively.Strains also increased the activity of soil urease,sucrase,and cellulase by 31.6%,26.6%,and 96.5%.According to the microbial diversity analysis,microorganisms increased the microbial diversity and richness of bulk soil.In the experimental group,the abundance of Streptomyces,Arthrobacter,Sphingomonas,Burkholderiaceae was higher than that of the control group,these strains were positively correlated with the content of TOC,TN,organic matter,available potassium,available phosphorus,urease and sucrase.