Study On Endophytic Actinomycetes And Bioactive Substance Against Tomato Leaf Mould Pathogen

Tomato leaf mould caused great damage in tomato product. It seriously happened recently in protected field. Endophyic actinomycetes are abundant microbial resource. They produce active metabolizing substance and were important significance in biocontrol of plant disease. In this study Endophytic actinomycetes were screened as biocontrol agent againt tomato leaf mould, which reduces production in vegetable yield.175 strains endophytic actinomycetes were screened in plate. 26 strains were antagonistic against Fulvia fulva, 14 strains against Botrytis cinerea, and 26 strains against Alternaria solani. Strain BAR1-5 was the most effective endophytic actinomycetes.In greenhouse experiment, the fermentation supernatant and mycelial suspending of 26 strains were tested to control tomato leaf mould on tomato seedling. Strains BAR1-5 was also the most effective agent, which control effect was 49.7%. And when applied behind and after its control effect also reached 50.6% and 62.6% respectively.In field experiment, the control effect of fermentation supernatant treat and its 5 times dilute treat still reached 42.5% and 33.1% respectively. The result above all suggested strain BAR1-5 was really a potential biocontrol endophytic actinomycete.According to its culture morphological, physiological, biochemical characteristics and analysis of the 16S rDNA, strain BAR1-5 was identified as Pseudonocardineae,and it was clustered to Pseudonocardineae,Pseudonocardiaceae,Goodfellowia in the Phylogenetic tree. Screen optimal fermentation medium and optimal culture condition for strain BAR1-5. The result of single factor test showed the optimal carbon, the optimal nitrogen and the optimum inorganic salt were 1% glucose, 0.2% yeast and 0.05% MgSO4 respectively. Based on the optimum factor above, the culture medium through orthogonal test was 2% soy powder, 0.5% corn powder, 1% yeast, 0.5% glucose and 0.08% MgSO4. The optimal fermentation condition: initial pH 7.2~7.5, 50mL medium in 250mL flask, culture time 144h.Study on the physical and chemical properties of bioactive substance produced by strain BAR1-5 indicated that, it was stable to UV, and relatively stable to middle temperature under weakly alkaline and neutral condition. It was dissolved in n-butanol entirely and ethyl acetate partly, but not dissolved in benzene and petroleum ether.The result of pH paper chromatography and paper electrophoresis indicated that the bioactive substance was amphoteric, its ion character was neutral, and close to non-water solubility typeâ…¡antibiotic.The result of UV spectrum, thin-layer chromatography and bioautography were all estimated that the bioactive substance contained at least three bioactive fraction. The studies provide valuable information for the further purification and structure determination...