Screening, Identification And Potential Of Biocontrol Of Antagonistic Bacteria Strains Against Phytophthora Capsici

Plant diseases are one of the main factors to disturb agricultural production. In recent years, vegetables are seriously influenced by plant diseases along with development of vegetable under structure and regulation of crop system. Oomycetes blight. virus disease, bacterial wilt and other major plant diseases have caused serious losses to solanaceae vegetables’production. Chemical pesticides are the main measures to control plant disease at present, which can make environmental pollution, pathogenic resistance to pesticides and do harm to non-target organisms. Plant diseases are controlled using endophytic bacteria with great potential. Research hotspot have arise at searching and discovering some new compounds with antibiosis from endophytic fungi and bacteria. Endophytes served as a kind of new microbe resource have been given extensive attention to this problem.Being aimed at pepper blight which occurred great area, caused serious harm, and it is difficult to control. Endophtic bacteria have been isolated from11plant vegetables.In this study, antagonistic bacteria strains have been screened, which can control efficiently pepper blight. Antifungal substances from endophytic antagonistic bacteria have been separated and part characters have been analyzed. Relationship between antagonism and prevention and therapy has been investigated. A theoretical basis has been provided for the research of endophytic bacteria. The results are as follows:1. There were79endophytic baeteria strains separated from11plant species, while24were from roots,37were from stem and18were from leaves.10antagonistic bacteria screened among79endophytic bacteria showed good antagonism against Valsa sordida, Botrytis cinerea, Cryphonectria parasitica, Pythium aphanidermatum, Rhizoctonia solani and Phytophthora capsici.2. In pot planting experiment. Strain LJ and XM inhibited Phytophthora capsici significantly. The inhibitory effect of LJ was stronger than XM. the control efficiency were71.18%and36.18%, respectively. When tested on postharvest fruits of capsicum and treated with the bacterial suspension, the control efficacy reached45.5%and63.6%, respectively.3. With the16S rDNA gene analysis, The strain LJ and strain XM were identified as number of genus Paenibacillus, Combined the BIOLOG MicrostationTM system analysis of strain LJ and strain XM, LJ was identified as Paenibacillus polymyxa and XM was identified as Paenibacillus jamilae.4. The fermentation filtrate of LJ and XM showed strong antagonistic activities to the zoosporangium formation and zoospore germination of P. capsici which made the mycelium become contorted and abnormality and even the protoplast fusion, reduce the germination of spores. And LJ and XM could also enhance the enyzme content of the capsicum. The result of biochemical determination showed that the enzyme activity of peroxidase (POD)、polyphenol oxidase (PPO) and phenylalanine amonnialyase (PAL) in fruits of capsicum increased. suggested that bacteria LJ and XM could induced resistance of the capsicum against P. capsici.5. The results showed that the active substances from LJ and XM were mainly lipophilic antibiotics.