| In recent years,land salinization has seriously limited the development of agriculture and the restoration of ecological environment in China.Under saline-alkali stress,plants will release a large amount of stress ethylene,leading to early senescence or death of plants.ACC deaminase-producing PGPR can reduce the amount of stress ethylene and improve soil salinity by degrading 1-amino cyclopropane-1-carboxylic acid(ACC),the direct precursor of ethylene.In this study of Daqing saline grassland rhizosphere soil as material,isolated the salinity tolerance of ACC deaminase strains,finally selected three strains of salinity tolerance and ACC deaminase ability are strong strains,the strains of strain identification and functional analysis,study the effect of strains of green bean stick root,through potted test validation strains of green bean plants and the influence on the soil environment,the main results are as follows:(1)Thirty life-promoting bacteria with the ability of producing ACC deaminase were qualitatively isolated from rhizosphere soil of Daqing alkali plant with ADF solid medium,No.,DQJC 1-DQJC30,By testing its ability to produce ACC deaminase and salinity tolerance,Finally,three highly comprehensive strains DQJC 1,DQJC 5,DQJC 6,The capacity of ACC deaminase produced in the three strains was8.147,7.282 and 7.906 U / mg respectively;All three strains were able to grow in LB medium at p H 11 and 10% Na Cl concentration,All three strains had the functions of IAA production,nitrogen fixation and phosphorus removal,Both expressed the acdS gene.After identification,the three strains were determined to be different species of Pseudomonas(Pseudomonas)(2)Under the condition of salinity and alkali stress,DQJC 1 and DQJC 6 could significantly reduce the ACC content in the root of mung bean.DQJC 1,DQJC 5 and DQJC 6 could significantly reduce the ACC synthase and ACC in the root of DQJC 6,which indirectly proved that the three strains could reduce the production of ethylene in stress.(3)In the pot experiment,inoculation of three life-promoting bacteria and compound bacteria could promote plant growth,simultaneously increased the antioxidant enzyme activity(SOD,POD,CAT,APX),reduced the membrane lipid content of peroxide peroxide(hydrogen peroxide,superoxide anion,MDA)in mung bean leaves and roots,increased the permeability content in mung bean leaves and roots(soluble sugar,soluble protein,proline),downregulated the ACC oxidase activity in mung bean root,effectively alleviated the toxicity of salt-alkali stress on mung bean,with better effect.(4)In order to explore the promoting mechanism of ACC deaminase on mung bean,test the influence of inoculation strain DQJC1 on lipid metabolism of mung bean leaves,61 significantly different metabolites were selected,of which 32 metabolites were glycerolipids;14 metabolites were glycerol lipids;4 lipids;7metabolites were other lipids;9 metabolic pathways were detected,the most significant change was arachidonic acid metabolism pathway,and the metabolites enriched in this pathway was lecithin,and the pathway with the most enriched metabolites was glycerol phospholipid metabolism pathway.(5)Under saline-alkali stress,DQJC1,DQJC5,DQJC6 and compound bacteria increased the content of urease,sucrase,phosphatase and catalase in the rhizosphere soil,increased the diversity and richness of soil microorganisms,and increased the relative abundance of beneficial bacteria in the soil to promote the growth of mung bean.In terms of bacteria,the relative abundance of Proteobacteria,Acitobacter,Bacteroidetes,Floating,Firmicutes,Actinobacteria,and Budnomonas increased in mung bean rhizosphere soil(Ascomycota)and Mediaria(Mortierellomycota)increased,while the abundance of unclassified＿k＿Fungi decreased.In addition,the inoculation of promoting bacteria increased the expression of acdS gene in mung bean rhizosphere,indicating that the three strains and complex bacteria could colonize in mung bean rhizosphere. |
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