Isolation,Screening And Functional Analysis Of Endophytic Bacteria With Ability To Improve Plant Growth And Drought Tolerance From Alhagi Sparsifolia

Drought,salinity,high temperature and other abiotic stress are important factors affecting the yield and quality of crops in arid areas.How to improve crop resistance to such abiotic stresses is always the focus of research.In recent years,with the discovery of plant growth-promoting endophyte bacteria,more and more researchers are trying to improve plant resistance and crop traits by digging out the endophytic strain and stress resistance gene.This study is based on Alhagi sparsifolia in north-west China,by isolationing and identificating the endophytic bacteria from different tissues of Alhagi sparsifolia,and excavating the plant growth-promoting endophytic bacteria and stress resistance gene,the main results are as follows:1.After sterilizing the tissues of Alhagi sparsifolia,a total of 164 strains of bacteria were isolated,of which,there were 69 strains in the root,50 strains in the stem,and 45 strains in the leaf,and these strains belong to 18families and 31 genera.2.Through the experiment of wheat seedlings,we find out 6 strains exhibit the ability to enhance the growth of wheat under drought stress.These strains are Enterobacter sp.LTJPAF-18F,Klebsiella sp.LTGPAF-6F,Pantoea alhagi LTYR-11Z,Pseudomonas sp.LTGT-11-2Z,Pseudomonas sp.LTJR-52 and Siccibacter sp.LTJR-64-2,The increment of fresh weight was between 46%-112%.Among them 4 strains had significant effect on the length of root and the increment was about 50%,but all the strains had no significant effect on the length of stem.3.We tested the characteristics of 6 strains to promote plant growth,these 6 strains all can produce NH₃;Klebsiella sp.LTGPAF-6F?Enterobacter sp.LTJPAF-18F?Pantoea alhagi LTYR-11Z?Pseudomonas sp.LTJR-52?Siccibacter sp.LTJR-64-2 can produce IAA and EPS;Enterobacter sp.LTPAF-18F?Pseudomonas sp.LTGT-11-2Z?Pantoea alhagi LTYR-11Z?Pseudomonas sp.LTJR-52?Siccibacter sp.LTJR-64-2 could produce siderophore;Enterobacter sp.LTJPAF-18F?Pantoea alhagi LTYR-11Z?Pseudomonas sp.LTJR-52 have the function of dissolving phosphorus;Klebsiella sp.LTGPAF-6F?Enterobacter sp.LTJPAF-18F?Pseudomonas sp.LTJR-52 can fix nitrogen,and most of strains can tolerate above 8%Nacl,10%PEG and 45?.These plant-promoting qualities might improve the drought resistance of wheat.4.We sequenced the whole genome of the strain Pantoea alhagi LTYR-11Z,and found out there were two luxI in the strain genome.Respectively,we construct the mutants of luxI-1and luxI-2,We found out after knocking out the luxI-2 alone,the ability of antioxidant,producing biofilm decreased and the ability of swimming increaced,the results indicated that luxI-2 can promote the ability of antioxygen and affect the interaction between plants and bacteria.But after knocking out the luxI-1 alone,there were no no significant effect on the strain Pantoea alhagi LTYR-11Z.5.After analyzing the whole genome of the strain Klebsiella sp.LTGPAF-6F,we identified genes related to the plant growth promotion and stress tolerance,such as nitrogen fixation,production of indole-3-acetic acid,acetoin,2,3-butanediol?spermidine and trehalose.This genes could confer the ability of strain C to improve plant growth and drought tolerance.