Screening Of Anti-FOC Race 4 Endophytic Bacteria From Banana And Identification Of Strain DB090208 And Its Control Effect Research

Fusarium wilt is a destructive soil-borne vascular disease of the banana, many countries had paid more attention to the biocontrol of the disease. In order to obtain satisfactory biocontrol agents for the production of services. This study rearch systematicly a endophytic bacteria which have the effect of wilt biocontrol by the parameters of the disease inhibition, conditions for fermentation, pot experiment against the pathogen.Use the potential biocontrol endophytic bacteria against Fusarium oxysporum f. sp. cubense race 4 as the target strains, thirteen strains within one hundred-fifty-seven isolates from the banana samples were obtained. They showed antagonistic effect against the pathogen, and the strain DB09208 was identified as Paenibacillus elgii exhibiting 74.7%and 87.9%of control effectiveness in plate and pot experiment respectively. Strain DB09208 inhibited mycelium growth and spore germination of F.oxysporum f.sp. cubense race 4 efficiently. It was identified as Paenibacillus elgi through the analysis of the morphological characteristics, cultural characteristics, physiological and biochemical characteristics,16S rDNA and phylogenetic.Results of microscope observation and UV absorption peak showed that extracellular metabolites of the strain DB09208 can cause swelling of FOC4 mycelium, vacuoles, damage the growing point, cause cells containing spills and inhibit spore germinationThrough the fermentation process optimization, the optimal medium composition and fermentation conditions of getting active substances of strain DB09208 were glucose 2.0%, sucrose 1.5%, yeast extract 1.0%, beef extract 1.5%, peptone 1.0%, K2HPO40.5%, MgSO4-7H2O 0.04%, initial pH7.0, seed age 48h,5% inoculation amount, the size 75mL in 250mL Erlenmeyer flask at 220 r/min and 30℃for 60h. The inhibition zone diameter of sterile filtrate of strain DB09208 increased from 16.5mm to to 20.5mm after optimization.Researching the characteristics of antibacterial compounds secreted by strain DB09208, the bioactive substance of DB09208 having heat, light and ultraviolet radiation stability were demonstrated. When the pH value of the fermentation broth was 3.0 to 9.0, the antibacterial activity changed a little, but when the pH reached 10, the activity disappeared.