Study On The Biocontrol Efficacy Of Endophytic Bacterium Em7 Isolate Against Sclerotinia Sclerotiorum On Oilseed Rape

The Sclerotinia sclerotiorum of oilseed rape is one of the major diseases of oilseedrape in the world. It is much severe in China. Biological control of sclerotinia disease, as an important alternative to chemical control, has received considerable attention due to the lack of resistant varieties, and increasing concerns over fungicide resistance in populations of S. sclerotiorum and fungicide residues in the environment. In recent years, fungal biocontrol agents were largely studed for the biocontrol of sclerotinia disease of oilseed rape. However, the report that this disease was controlled with endophytic bacteria is few. So, effects of endophytic bacteria isolated from winter wheat on S. sclerotiorum were studied in this thesis.The main results were as follows:1. Through dural culture assay, endophytic bacterium Em7 isolate was screened out from 63 isolates on PDA medium, which should strongly inhibit the growth of S. sclerotiorum. It also should inhibit the formation of sclerotia and the germination of sclerotia. The results showed the inhibitory rate dereased with the increasing of times of dilution of Em7 filtrate by the means of the liquid culture.2. In greenhouse experiments, the filtrate of Em7 isolate had 95.73% control effect against S. sclerotiorum. The biocontrol efficacies were different by spaying filtrate of Em7 in different time. Before 24h of inoculation S. sclerotiorum, the biocontrol efficacy was highest 93.28%; it was lowest by spaying Em7 filtrate after 24h of inoculation S. sclerotiorum. Different times of dilution of filtration had different effects on the biocontrol efficacy. With the increasing of times of dilution of Em7 filtrate, the biocontrol efficacies decreased.3. Antagonistic bacterium Em7 isolate had the broad-spectrum inhibitory effect to plant pathogens. By the means of the liquid culture, the results indicated that cell free filtrate of Em7 isolate had more than 50% inhibition rate against 22 pathogens. It should also strongly inhibit the germination of spores of 4 pathogens. The Em7 filtrate had 81.20% and 71.36% control effect against Blumeria graminis f.sp. tritici and Puccinia striiformis f.sp. tritici in glasshouse trials.4. Antagonistic bacterium Em7 isolate induced diverse morphological alterations in...