The Biocontrol Of Vegetable Gray Mold (Botrytis Cinerea Pers.) By Antagonistic Actinomycete E001Strain

The gray mold caused by Botrytis cinerea is one of the important plant diseases through out the world, and it makes ruinous harm to greenhouse vegetables especially to tomato. Chemical control of gray mold has become increasingly diffcult due to the problem of resistance of the pathogen Botrytis cinerea to fungicides as well as the increasing concern of environmental pollution as a result of chemical fungicides. The E001strain was obtained as a antagonistic actinomycete against Botrytis cinerea. Then the identification of E001strain, the optimization of fermentation condition, the stability of the free-actinomycete filtrate (FAF) of the strain, the mode of action against Botrytis cinerea and the biocontrol efficacy of the FAF of E001strain against Botrytis cinerea were studied.1. Four huandreds and twenty actinomycetes strains were screened from4soil samples with dual-culture test, and15strains among them were with strong antagonism and the strain E001was defined as a candidate against Botrytis cinerea.2. According to the methods of actinomycete classification, the cultural characteristics, the mycelium morphology, the physiological and biochemical characteristics were observed and the16S rDNA sequence of strain E001was determined in this paper. The results indicated that the strain E001was identified to be Streptomyces scabies.3. The experiments of optimum fermentation medium and fermentation condition of strain E001were carried out. The results showed that the optimum fermentation medium of strain E001was Millet leaching juice medium, and the optimum carbon and nitrogen sources were sucrose and beef extract respectively. The optimum fermentation conditions were the initial pH7.5, the temperature28℃, the time4days, the inoculation volume6%, and the rocker rotational speed220r/min. 4. The FAF of strain E001had a good stability to ultraviolet irradiation. The antibiotic activity of the FAF of strain E001against Botrytis cinerea was decreased with the temperature rising. The antibiotic activity was the highest in the FAF of pH6.5(the nature pH value), and it was decreased with the pH value rising or decreasing. The FAF of strain E001had a better stability when stored at4℃than at room temperature, and the antibiotic activity was decreased significantly after20days of storage.5. The mode of action of strain E001against Botrytis cinerea was observed. The results showed that the strain E001strongly suppressed the growth of Botrytis cinerea mycelium. The mycelium was made tumescent, abnormal, the vesicle expanded, the branching increased, and the plasma leaked out after treated by the FAF of strain E001. The FAF of strain E001strongly inhibited the germentation of conidia of Botrytis cinerea. The conidia germination suppression rates were99.38%and97.31%in2-fold and10-fold diluent of FAF of strain E001respectively.6. The prevention efficacy of the FAF of strain E001on gray mold in leaves and fruits in vitro were all above99%, in which the prevention efficacy of the FAF of strain E001in cucumber fruits in vitro was obviously higher than that of carbendazim50%WP500-fold dilution. The therapeutic efficacy of the FAF of strain E001on gray mold was from56.75%to76.81%. The FAF of strain E001had remarkable prevention and therapeutic efficacy against tomato gray mold in vivo. The prevention and therapeutic efficacy of the E001FAF reached94.77%and93.84%respectively at10days after treatment, both obviously higher than those of carbendazim50%WP500-fold dilution, which were55.81%and68.42%.