Isolation And Identification Of Plant Growth Promoting Rhizosphere Bacteria Under Drought And Salt(abiotic)stress Conditions In Cotton

Drought and salt stresses are important factors affecting crop production,distribution and yield.Microbiome is considered to be the second set of plant genome,which is very important for plant growth and stress adaptation.In this study,the composition of cotton rhizosphere bacteria,the types of bacteria which are beneficial to salt tolerance and drought resistance,and their functions were studied.The main results are as follows:The interaction between PGP bacteria and cotton under salt stress was studied.Firstly,the rhizosphere bacteria were isolated and cultured under the salt stress of cotton,and the bacterial strains such as Bacillus subtilis(BB)and Bacillus pumilus(BC)were successfully obtained.Then these strains were applied to the rhizosphere of cotton under salt stress(200m M Na Cl).It was found that BB and BC could enhance the resistance of cotton to salt stress,which was manifested in the root,stem and leaf of cotton plants with BB or BC.The study further sequenced the transcriptome of cotton roots under salt stress of BB or BC treatment.The results showed that there were 5535 differentially expressed genes,3349 up-regulated genes and 2186 down-regulated genes in the presence or absence of Bacillus subtilis(S versus BB),and 8452 in the presence or absence of Bacillus pumilus(S versus BC),including 4035 up-regulated genes and 4417 down-regulated genes.GO analysis showed that these genes were differentially expressed in the intrinsic component of membrane,integral component of membrane,the activity of DNA binding transcription factors,the activity of membrane part and oxidoreductase.When BB and BC were provided respectively,the interconversion of pentoseglucoronate and the metabolic pathway of starch-sucrose were considered to play an important role in improving plant growth under salt stress.The effect of drought on the microbial composition of cotton rhizosphere was studied.In this study,soil collected from cotton field was used to grow cotton under controlled environment(Gossypium hirsutum cv.Jin668).At the flowering stage the drought stress was applied(SDP),while the control plants(SPN)were watered regularly;meanwhile,soil with drought treatment(SOPD)and control soil(SNPN)were set.After 2 weeks of water cut-off,samples were collected from rhizosphere soil and root surface soil in sterile tubes to isolate microbial DNA,and 16 S r RNA gene was sequenced in high-throughput.Compared with the soil without plants,the α diversity of bacteria in the soil with cotton plants increased significantly.Taxonomic analysis showed that the bacterial community structure of cotton rhizosphere was mainly composed of Proteobacteria,Actinobacteria,Gemmatimonadetes,Chloroflexi,Cyanobacteria,and Acidobacteria.In the rhizosphere of drought treatment,Chloroflexi and Gemmatimonadetes were the dominant.This study shows that even under drought stress,cotton rhizosphere has a rich bacterial community,which may improve the drought tolerance of plants.These data will support the future improvement of cotton drought tolerance through soil microbial community.