Screening Of Salt-Tolerant And Growth-Promoting Strains And Their Remediation Effects On Salinized Soil Of Greenhouses

The soil salinization is the main form of cultivated soil degradation.Repairing the soil salinization is the key to ensuring sustainable development of agriculture in our country.Microbial remediation is one of the remediation measures of salinized soil,and its application effect depends on the salt-tolerant and growth-promoting ability of microorganisms.Therefore,on the basis of comparative analysis of the microbial flora structure of healthy field soil,coastal saline soil and greenhouse saline soil,this study took salinized soil as material,using high salt medium and growth promotion method to screen salt-tolerant and growth-promoting strains,and applied them to greenhouse salinized soil to verify the repair effect,laying a foundation for the repair of salinized soil with microbial agent.The main results were as follows:1)The chemical properties and microbial diversity of coastal saline soil,greenhouse saline soil and field healthy soil were compared and analyzed.The results showed that Chloroflexi and its genera,Ascomycota and its genera such as Trichocladium and Fusarium were the dominant microbial groups in saline soil.Firmicutes also increased in abundance in salinized soil.Correlation analysis showed that conductivity and total salt were the main factors affecting microbial diversity and community composition.conductivity and total salt were positively correlated with unclassified＿A4b,unclassified＿Chloroflexi,unclassified＿Alphaproteobacteria,Trichocladium,Cephaliophora,and Sodiomyces.2)Fifty-eight salt-tolerant strains were isolated from 37 salinized soils using LB medium with 5%salt content.The effect of strain on seed germination was measured under 1%salt stress.Compared with water control,the simplified activity index of strain YQ-1-8,SN-1-4,3A-2,L1-2 and L3-3 increased by more than 15%.Vermiculite plate growth promotion experiments were conducted on 5 strains under different salt concentrations（0,0.3%,0.5%,1%）.The results showed that,The five strains had good growth promoting effect under salt stress.3)Through morphological,physiological,biochemical and molecular biological identification,YQ-1-8 was Bacillus velezensis,SN-1-4 was Arthrobacter arilaiti,3A-2was Bacillus marisflavi,L1-2 was Bacillus cereus and L3-3 was Bacillus aryabhattai.The analysis of salt-tolerant and growth-promoting properties of the five strains showed that all the five strains had good salt tolerance,organophosphorus hydrolysis,indoleacetic acid production and extracellular polysaccharide production.4)The remediation effect of Bacillus marisflavi 3A-2 on salinized soil was measured by pot experiment.The soil remediation effect was the best when the concentration was1×10⁷ cfu·g^-1.Stem diameter,plant height,chlorophyll,aboveground fresh weight and dry weight in treatment group were significantly higher than those in control group.Soil alkali-hydrolyzed nitrogen and available potassium were significantly increased by 4.49%and 4.91%,respectively.While soil p H,conductivity and total salt were significantly decreased by 0.96%,16.45%and 16.84%,respectively.There was no significant change in the soil bacterial community,but the abundance of Ascomycota and its genera such as Trichocladium in the fungal community increased,and the microbial interaction was closer and more stable after the treatment of the bacterial agent.