Screening And Diversity Analysis Of Plant Growth Promoting Endophytic Bacteria From Peanut

Endophtic bacteria reside within the inner parts of various plant hosts without causingdisease symptoms.They influence each other and form an organic unity. Many endophticbacteria are beneficial microbial resources for improving plant growth and abilities ofantidisease and antiadversity. In order to screen the plant growth promoting endophyticbacteria isolates of peanut and obtain the bacterial strain with proprietary intellectual propertyrights, the IAA-producing stains, antagonistic stains and siderophore-producing stains wereisolated from the peanut plant. The peanut plants were sampled at young seedling stage,beginning peg stage, full pod stage and harvest maturity stage respectively. The geneticbiodiversity and population changes of the endophytic bacteria were investigatedpreliminarily by using the analysis of16S-RFLP and16S rDNA sequences.The satisfactory disinfection efficacy was obtained as following method:75%ethanol for3min,3%sodium hypochlorite （NaClO） for2min, then75%ethanol for30s.The peanut endophytic bacteria were isolated by the R2A media. The numbers ofendophytic bacteria at different peanut growth stages were found to range from2.6×104cfu/gFW to7.1×104cfu/g FW, with the maximum at the full pod stage the minimum at the harvestmaturity stage.94isolates were obtained based on phenotypic characterization andmicroscopy. There are22,28,30and14isolates from young seedling stage, beginning pegstage, full pod stage and harvest maturity stage respectively. By the RFLP analysis of16SrDNA （16S-RFLP）, the94isolates were divided into29clusters or genotypic groups at100%similarity, and14groups at92%similarity. A total of31representative isolates were selectedfrom each cluster according to the dendrogram of the16S-RFLP and sequenced. The resultsshowed that the isolates were clustered into14different genera, which were further dividedinto at least26different species. Bacillus was the dominant genera and was detected in everygrowth stage. Many distinctive genera were obtained in some growth stages, such asRhizobium, Microbacterium and Burkholderia were found only in the harvest maturity stage;Exiguobacterium and Acinetobacter only in the beginning peg stage; and Enterobacter andFlavobacterium only in the young seedling and full pod stages, respectively. There are alsorecurring isolates from the peanut plants, such as Arthrobacter which appeared at the young seedling stage and the full pod stage but disappeared at other two stages.There are48IAA-producing strains,14antagonistic strains and3siderophore-producingstrains we got. Quantitative analysis revealed that the high-level (>50mg·L^-1·OD600^-1)IAA-producing strains were Bacillus, Pantoea, Enterobacter and Rhizobium. Among the14antagonistic isolates,12strains were known to express antimicrobial activity against the fourpathogenic fungi, namely, Fusarium solani, Colletotrichum gloeosporioides, Botrytis cinereaPers, and Pseudoperonospora cubensis and only two showed weak inhibition againstSclerotium rolfsii. And the3siderophore-producing strains all belong to Pseudomonas. Twostrains have ability to production of siderophore, production of indole acetic acid andantagonistic;11bacteria can produce indole acetic acid and antagonistic. We got51growth-promoting and antagonistic bacteria. It laid the foundation for the development andapplication of the strain resources.