| In this study,ACC deaminase-producing bacteria were screened from the rhizosphere soil of Halostachys caspica in the saline-alkali land in Wujiaqu,Xinjiang,and their ACC deaminase activity and salt-alkali-tolerant ability were determined.Strains with high ACC deaminase activity and excellent salt-alkali tolerance were selected,and identified through morphological observation,physiological and biochemical experiments,Biolog identification,and 16 Sr DNA sequencing analysis.The strains were tested for their ability to fix nitrogen,produce IAA,dissolve phosphorus,and produce siderophores,then made a single strain and mixed bacterial solution to treat corn and melon seeds,and evaluate the promoting effect of bacterial solution treatment on corn and melon under salt-alkali stress.A plasmid with tetracycline resistance and green fluorescent protein genes was constructed and successfully transferred into the tested strains to carry tetracycline resistance and green fluorescent double markers,so as to further explore the identification of the marker strains in the rhizosphere of corn and melon.Reproduction situation.The results of this study are as follows:(1)After directional screening of the medium,multiple isolation and purification,a total of 10 strains with ACC deaminase activity with different colony morphology were screened out from three soil samples;three strains W5,W8,and W9 were screened out The strain ACC is a strain with high deaminase activity and excellent salt-alkali-tolerant performance;after identification,the three strains were named Brevibacterium casei W5,Brevibacterium casei W8,Rhizobium pusense W9.(2)Three strains of W5,W8,and W9 have the ability to fix nitrogen,and strain W9 also has the ability to produce IAA;through seed growth experiments,it was found that alkali stress had no significant effect on the germination rate of corn and melon,but had no significant effect on the germination rate of corn and melon.The three indexes of main root length and root amount have certain influence.Inoculation bacterial liquid can promote the growth of corn and melon under alkaline stress in the p H range of 7-11,and the effect of mixed bacterial agents is better than that of single bacterial agents.Salt stress has a significant effect on the germination rate,bud length,main root length and root amount of corn and melon.With the increase of salt concentration,the germination rate,bud length,main root length,and root amount of corn and melon decreased significantly.In the range of 0%?2% salt(Na Cl)concentration,the inoculation bacterial solution can promote the growth of corn and melon under salt stress,and the effect of mixed bacterial agents is better than that of single bacterial agents.The growth-promoting ability of the two strains W5 and W9 on corn and melon under salt-alkali stress is not significantly different.(3)The strain resistance experiment found that the strain W5 is resistant to100?g/m L ampicillin,25?g/m L streptomycin and 10?g/m L tetracycline,and W9 is resistant to 100?g/m L ampicillin and 50?g/Ml Streptomycin is very sensitive to tetracycline;a GFP-p BR322 plasmid with green fluorescent protein gene and resistance to tetracycline and ampicillin was successfully constructed.The constructed plasmid was successfully transferred into E.coli DH5? competent by heat shock method.The Spizizen method successfully transferred the plasmid into W5,and the plasmid was successfully transferred into the W9 strain by repeated freezing and thawing methods,and the introduced plasmid could be stably inherited in the three strains.The inoculation of bacterial suspension can effectively promote the growth of corn in saline-alkaline soil,and the growth-promoting effect of mixed strains is better than that of single strains.Melon cannot grow in saline-alkaline soil regardless of whether it is inoculated or not.And got the colonization of the strain in the rhizosphere soil of corn and melon. |
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