Screening, Identification of Antagonistic Organisms Against R. Solanacearum and Effect of Their Bio-Organic Fertilizer of Eggplant
|School||Nanjing Agricultural College|
|Keywords||bacterial wilt of eggplant antagonistic bacteria bio-organic fertilizer biocontrol|
Eggplant bacterial wilt, caused by Ralstonia solanacearum, is a common and destructive disease of greenhouse and field-grown eggplant in China and worldwide.The disease caused serious economic losses. Breeding of culitvars with resistance to bacterial wilt, chemical application and field management are among the solutions to control this disease. However, it is necessary and urgent to find a better way to ensure banana industry worldwide. Biocontrol has been proven to be economical and environment-friendly for overcoming such soil-borne disease. Antagonistic strains against bacterial wilt were systematically studied on following aspects:isolation, screening, identification and biological characterization of the antagonistic strains, control effect of the derived bio-organic fertilizer under greenhouse, Action mechanism. Results were showed below:The strainⅡ-36, which showed high antifungal activity against R. solanacearum, was obtained from the healthy rhizosphere and bulk soil in the eggplant plantation that was seriously infected with Bacterial wilt (R. solanacearum). Results from morphological and physio-biochemical identification and 16S rDNA sequence analysis showed that the strain belonged to Bacillus subtilis. The optimal fermentation conditions for strainⅡ-36 were: temperature at 30℃, initial pH value 7.0, glucose as carbon source, and peptone or glutamic acid as nitrogen source.The soil and eggplant seedlings were treated with the antagonistⅡ-36 and their effects were studied in the greenhouse. The mixture of pig manure compost and amino acid fertilizer was inoculated with 20% (V/W) of II-36culture and fermented for 4 days to produce a bio-organic fertilizer (BOF).The results obtained were listed as follows. Application of the bio-organic fertilizers (BIO-36 and BIO-23) significantly increased fresh biomass and root activity of eggplant seedlings after grown in nursery cups for 30 days. The bio-organic fertilizer inhibited the eggplant wilt disease (antagonistic effect, respectively,96% and 91%). The activities of antioxidases (catalase, peroxidase and superoxide dismutase) in eggplant leaves were significantly higher, but the content of MDA was reduced remarkably. CAT activities for BIO-36 and BIO-23 were increased by 25.0% and 23.7% respectively as compared with the control, the activities of POD were increased by 99.5% and 93.6% and that of SOD were increased by 32.7 and 29.8%, respectively, while the contents of MDA were decreased by respectively 29.5% and 26.3%, respectively comparing with control. In addition, the application of bio-organic fertilizer changed microbial communities in rhizosphere soil: significantly decreased the number of Ralstonia solanacearum, increased fungi and actinomycetes, smaller changes in bacteria. The application of the bio-organic fertilizer at seedling and greenhouse could significantly promote the growth of eggplant plants and suppress bacterial wilt, improved the survival of strainⅡ-36.The optimal medium and fermentative condition ofⅡ-36 was researched in this study. The results showed that optimal medium was LB medium. The optimal fermentation condition ofⅡ-36 was pH8.0,30℃～34℃,50mL/250mL.One of the protein was purified by using ammonium sulfate Preeipitation, the best saturation was 90%. The antibaeterials ubstances was found to bet hermostable. The antagonistic protein was insensitive to environment heat such as:at 100℃,121℃30 min antagonistic abilities were 59.2%、46.8%, at pH9 and pH11, antagonistic abilities were 92.1%、63.8%.It was not sensitive proteinase and pepsin. The antibacterial substances of strain 11-36 could to lower the EPS secretory volume of Ralstoniasolaneearum. Thanmore, the strain 11-36 could produce siderophores.