Effects Of Salinity-tolerant Growth-promoting Bacteria On Mung Bean Growth And Rhizosphere Microecology

In recent years,the degree of soil salinization in Daqing has been gradually intensified.Microbial improvement of saline-alkali soil is a hot research topic now.PGPR(Plant Growth Promoting Rhizobacteria)can improve plant root microenvironment,promote plant growth,and enhance the resistance of plants to stress,and ultimately achieve the effect of modified saline soil.Most of the PGPR that were screened in neutral soils were difficult to survive and play under saline-alkali stress.In this study,we used the Artemisia scoparia and Suaedaglauca Bunge rhizosphere soil in the saline-alkali soil of Daqing as materials,compared their bacterial community structures,screened and identified saline-alkali tolerance and growth-promoting bacteria,a pot experiment was conducted to test the effects of single and compound bacteria on the growth of mung bean plants under saline-alkali stress,varieties of rhizosphere soil microbial community and bacterial metabolic function were analyzed by using high-throughput sequencing technology and Biolog-Eco method.The results were as follows:(1)Available nitrogen,available nitrogen content in rhizosphere soil of Artemisia scoparia and Suaedaglauca Bunge were higher than bulk siol,and the p H of them was lower than bulk siol.The unique dominant bacteria phyla in the rhizosphere soil of Artemisia scoparia,Suaedaglauca Bunge rhizosphere soil and bulk soil were Acidobacteria,Cyanobacteria and Actinobacteria,respectively.The dominant bacteria genera in the rhizosphere soil of Artemisia scoparia were Pontibacter,Pseudomonas,Ohtaekwangia and Flavobacterium,and the dominant bacteria genera in the rhizosphere soil of Suaedaglauca Bunge were Pontibacter,Adhaeribacter,Massilia and Flavobacterium,the dominant bacteria in the bulk soil were Pontibacter,Gillisia,Lysobacter and Cesiribacter.In phylum level,the number of differential species in rhizosphere soil of Artemisia scoparia was 9,in rhizosphere soil of Suaedaglauca Bunge was 3,and in bulk soil was 8.The three kinds of saline-alkali soil bacterial community structures were different.(2)Screening of saline-alkali tolerance and growth-promoting bacteria in the rhizosphere soil of Artemisia scoparia and Suaedaglauca Bunge,30 strains which had different promotion functionsawere screened,and the strain KM1 could fix nitrogen,dissolved inorganic phosphorus and organic phosphorus.,produced ACC deaminase and indole-3-acetic acid(IAA),the strain NM8 could fix nitrogen,dissolved inorganic phosphorus,produced ACC deaminase and IAA.Through physiological and biochemical identification and phylogenetic analysis,KM1 was identified as Serratia,NM8 was identified as Bacillus.(3)Planting mung bean in saline-alkali soil,by inoculating saline-alkali tolerance and growth-promoting bacteria KM1,NM8,S29 and compound bacteria,root fresh weight and dry weight of mung bean had been significantly increased,and the compound bacteria treatment increased by 31.22% and 29.55% respectively,and the application of growth-promoting bacteria reduced the activities of SOD,POD and CAT in the roots of mung bean,and increased the soluble sugar in the mung bean plant,soluble protein and proline content.(4)Strains KM1,NM8,S29 and compound bacteria inoculation treatment increased the alkaline phosphatase activity of mung bean rhizosphere soil by 5.61%-25.23%,and the invertase activity increased by 14.67%-34.78%.Except strain KM1,the other 3 treatments the soil urease activity of the soil increased,and the soil invertase and urease activities of the compound bacteria were 1.35 times and 1.16 times that of the control,respectively.The application of growth-promoting bacteria could enhance the carbon source utilization capacity of mung bean rhizosphere soil bacteria.Rhizosphere soil bacteria under KM1,NM8 and compound bacteria treatments had higher utilization rates of the six carbon sources than that of the soil without inoculation treatment.Soil under S29 treatment bacteria had a high utilization rate of 5 kinds of carbon sources,but a low utilization rate of phenolic acid carbon sources.(5)Under saline-alkali stress,S29,KM1 and NM8 could colonize mung bean rhizosphere and increase the diversity and abundance of soil bacteria.They could also promote the growth of mung bean by increasing the relative abundance of beneficial bacteria in the soil.Through Lefse and LDA analysis of soil landmark species,there were 9 in CK,6 in S29,9 in KM1,5 in NM8,and 15 in S+N+K.In the analysis of the entire network relationship,the nodes in the compound bacteria were the most,and the interaction relationship between the flora was the strongest.