| Daqing City is located in the Songnen Plain in Heilongjiang Province and the land is highly salinized.The saline-alkali soil contains a large number of salt-tolerant strains,some of which have special growth-promoting functions and may be used as beneficial growth-promoting bacteria to promote plant growth and enhance the resistance of plants to saline-alkali.In this study,the saline-alkali soil in Daqing area was used as the experimental material to isolate salt-tolerant growth-promoting bacteria,select strains with better growth-promoting effects for strain identification.Meanwhile,the growth-promoting effects under salt-alkali stress conditions were verified with red adzuki bean seed germination and cuttings tests.The compound bacteria with good growth-promoting effects were selected to carry on the pot experiment of red adzuki bean in saline-alkali soil.The main conclusions are as follows:43 strains of different morphological salt-tolerant bacteria were isolated from the saline-alkali soil,then the isolated strains were qualitatively and quantitatively rescreened for their growth promoting functions.5 Strains with the better ammoniaase function were identified,which the No.29 strains were identified as bacteria of the genus Zobellella,and the other 4 strains were identified as bacteria of the genus Halomonas,which 5 strains were used in growth-promoting test of red adzuki beans.Taking the adzuki bean cuttings,inoculate 5 strains of single bacteria and select 3strains to make two combinations of T1 and T2 inoculants.To verify the growth-promoting effect on the lateral rooting of adzuki bean cuttings under salt-alkali stress,the results showed that the inoculation of salt-tolerant growth-promoting bacteria can significantly increase the number and length of the lateral roots of adzuki bean cuttings under salt-alkali stress,promote the growth of adzuki bean roots,and alleviate the inhibitory effect of salt-alkali stress on the growth of adzuki bean.Planting the adzuki bean seeds in saline-alkaline soil,and irrigating the better growth-promoting effect of the compound T1 was selected.Samples were taken after40 days of normal culture,the results showed that the fresh weight of adzuki beans,dry weight of shoots,plant height,number of leaves,chlorophyll content and leaf area increased by 48.04%,57.62%,35.45%,32.86%,31.50% and 50.94% after inoculation;After inoculation,the root length,dry root weight,fresh root weight and root volume of the treated group were significantly increased by 90.49%,118.64%,105.02% and294.81% compared with no inoculation group;the SOD,POD,CAT and APX activities and MDA content of the red bean plant leaves and roots were significantly reduced after inoculation;the content of soluble sugar,soluble protein and proline in the leaves and roots of the plant was significantly increased by 28.9%,34.89%,107.21%,50.0%,307.48% and 94.2%;the root vitality of the plant was significantly higher than that of no inoculation,and increased by 69.62%;the antioxidant enzyme-related genes in the leaves were all down-regulated,and the application of microbial agents had a significant effect on the expression of antioxidant enzyme-related genes in the adzuki bean leaves.The compound microbial agent was applied to the soil of planting red adzuki beans,which the physical and chemical properties of the soil were found to have changed after 40 days.The soil p H and soluble salt content were significantly reduced,which effectively alleviated the degree of soil salinization;the content of available nutrients in the soil such as alkali decomposable nitrogen,available phosphorus,available potassium and various soil enzyme activities have been significantly increased,and created the suitable living conditions for the growth and development of plants.The soil bacterial diversity of red adzuki beans inoculated after the application of the compound bacterial agent was determined,which the main bacterial phyla was Proteobacteria and Actinobacteria.Compared with the soil without inoculants,the diversity and abundance of microbial communities were significantly different.The application of the growth-promoting bacteria greatly improves the diversity and abundance of soil bacterial communities.The analysis results of the bacterial community level showed that the abundance of bacteria such as Nitrospira and norank?c??Actinobacteria increased significantly with the application of inoculants.The soil fungi diversity of red adzuki beans inoculated after the application of the compound inoculum was tested,which the main fungal phylum was Ascomycota,Zygomycota and UN-k-Fungi.Through LDA analysis and Lef Se analysis of the different species of fungi at each level in the two treatments,the results showed that the control soil in the Ascomycota phylum Nectriaceae and its subordinate Fusarium were significantly enriched,while the relative abundance of Mortierella in the soil treated with the microbial agents increased significantly.In this study,several saline-alkali-tolerant bacterial with plant growth-promoting ability were isolated and identified in the Daqing grassland saline-alkali soil.The plant growth-promoting effects of the single bacteria and compounds inoculants were tested through indoor and outdoor experiments.The experiment also found that the compound growth-promoting bacteria agent can significantly improve the physicochemical properties of red adzuki bean rhizosphere saline-alkali soil and enhance the saline-alkali resistance of plants,which can promote plant growth when applied to saline-alkali soil. |
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