Screening Of Antagonistic Bacterium Against Magnaporthe Grisea And Pre-extraction Of Bioactive Metabolite

Rice blast was the most serious rice disease in Heilongjiang province,and brought the adverse effect to rice yield and quality. Biological control with its no pollution, no residue become the prevention and treatment of rice blast. But there are many problems on the whole, such as single function, the control effect of biocontrol agents is not stable,and the production and application is not perfect. So selecting a strain with high efficiency and broad spectrum biocontrol,and mixing with low toxicity pesticide not only can solve the above problems, but also can improve the problem that produced by the chemical control such as resistance, residual pollution, thus can effectively improve the control effect of disease.579 bacteria were isolated from rice rhizosphere soil in 16 counties of Heilongjiang province by way of streak on plate method,then through plate confrontation test and punched method screening, 23 strains of antagonistic bacteria with inhibition rate above 50% were selected out, accounting for 4% of the number of individuals separated.A strain of Sc2 was showed to have strong inhibitory activity against Magnaporthe grisea,with the inhibiton rate of 73.44%. Antibacterial spectrum experiment results prove that, the inhibition of all the tested pathogens were above 60%. So Sc2 with the potential as bio-control strains has high efficient and broad-spectrum antibacterial effect.After a series of identification, the strain Sc2 was Bacillus subtilis. The best fermentation formula were selected: yeast extract 0.5%, glucose 0.3% and Nacl 0.5%. The inhibitory diametera increased to 35.64 mm and the inhibiton rate was 79.20%.A series of diluted culture supernatant of the strain Sc2 from 1~200 showed strong inhibitoyr activity against the hypha gorwth and spore germination of M. Grsie. With the increase of dilution ratio, inhibitory activity was gradually decline.The hpyha can hardly grow at 5X and 10 X, even 20.1, 10 times diluent on rice blast hyphae growth inhibition rate were above 80%. The inhibition rate of 40 times diluent of spore germination after 24 h and hypha gorwth on 7d was more than 60%.The Sc2 had good compatibility with tricyclazole, the 4000 ug/mL of tricyclazole concentration can still grow.In seeding stage pot experiments,the control effects of spraying the Sc2 filtrate were mainly conrtibuetd by perventing activity. The Sc2 and tricyclazole 1:2 ratio of the control effect is significantly higher than other treatment,with the inhibition rate was 90.33%.Though the Sc2 filtrate treated seeds, germination rate were no significant difference compared with control. It means the Sc2 filtrate had no effects on rice seed germination. The Sc2 filtrate can significantly improve the growth of rice seedlings with potted and hydroponics conditions, especially on the rice root growth, 5 of root dry weight growth rate of 175% and 137.9% respectively.One crude protein from ammonium sulfate at 40%~50% saturation(do not contain 40%) showed signicfinatly inhibited activities to M. grsiea, with the inhibition rate of 63.02%.The antifungal activity was decreased 4.30% and 9.34% after treated with trypsin and proteinase K respectively.