Studies On Optimization Of Fermentation Conditions And Biocontrol Effects Against Fusarium Solan Of Bacillus Subtilis D221

Bacillus subtilis strain D221 is isolated from rhizosphere of pepper by Pesticides lab of Northeast Agricultural Univerdity. Strain D221 showed antagonistic activity though plate inhibition method and pot culture trails against hot pepper root rot. On the basis of studies,this disseration is focused particularly on studies on fermentation condition optimization,test of stability of fermentation broth,control efficacy of Bacillus subtilis D221 against hot pepper root rot in the greenhouse.The main results are as follows:1.Optimized the liquid fermentation medium and technological conditions of Bacillus subtilis D221,The results showed that optimum medium formula was Sucrose 2.0%,Trgprotein 0.5%,Beef 2.0%,NaCl 0.5%,MgSO4 0.1%. The favorable fermentation condition was determined: The optimal fermentation parameters were 30℃,150 r/min, 5% inoculation volume,initial pH value of medium 7, and 30mL culture in 250mL flask for 48h,which had the strongest antagonistic avtivity. Under this optimized condition,the inhibition zone diameter increased 66.7%to the initial condition.2.Studied on the stability of UV,natural light,different temperature,different pH,reservation.The results for antibiotic physicochemical property of strain D221 showed that the active substance was stable to natural light and ultraviolet irradiation; It was also relatively stable to the hyperthermia around 80℃while the inhibition activity falls down at 100℃; .Prtial stability to acid or alkali, unstability to high alkali condition; and Storage stronger .3.By means of mycelium growth rate we measured the antibiogram of D221 strain, its fermentation products were against Sclerotinia sclerotinorum, Fusarium oxysporum, Rhizoctonia solani, Verticillium dahliae, Bipolaris sorokiniana, Phytophthora sojae.The results showed that the fermentation products of D221 can resist many plant pathogenic fungus.4. Pot experments in greenhouse showed that the cell-free filtrate of D221 fermentation have a good control efficacy to the hot pepper root rot in seedings after inoculated with pathogen. Using strain D221 cell-free filtrate 48h, 24h and 0h defore inoculation, the biocontrol efficacy were 96.8%,88.4% and 77.4% respectively investigated 7d after inoculation. The biocontrol efficacy was 80.3%,56.6% and 37.5% respectively 14d after inoculation. The result showed that strain D221 was a potential biocontrol agent in hot pepper root rot control.