Inhibition Mechanisms Of Extracts From Microorganisms Against Phytophthora Infestans

In order to effectively control potato late blight using microbial material, different antagonistic microoganism strains were selected according to their inhibiton effects on growth of Phytophthora infestans (Mont.) de Bary by using dual-culture method. Among 36 species, 16 species showd the evident inhibition effects. The inhibition rates of B3282, Bacillus sp., and A32810 were more than 70%, and rates of A4228, A32912, A5253, and A32914 were more than 60%. However, there were only fermentations from 3 of 36 species, A. brassicae, A. kikuchiana, and A32914 displaying markable suppression. And their inhibition rates were 80.51%,70.20%, and 48.91%, respectively.The inhibitory effects of combination fermentations on the hypha growth of P.infestans were also investigated. The results showed that some combinations'inhibitory effects were between the single fermentations' inhibition, which did not show significantly synergistic or cooperation inhibition to P. infestans; some of combination fermentations from two species microorganism's fermentations showed significantly synergistic or cooperation inhibition to P.infestans. The treatmet of A. brassicae fermantation in combination with A. kikuchiana fermantation had the strongest inhibition, and the rate of which reached up to 90.38% higher than that of the single fermentation.We also studied the inhibition mechanisms from single A. brassicae fermantation, A.kikuchiana fermantation and their mixtures on P.infestans. The results showed that:all of the single fermentations and their mixtures had inhibition on protein synthesis of P. infestans' mycelium, zoospore release and zoospore germination of P. infestans.The crude antagonistic substance which from A. brassicae fermentation was stable to pH and heat. The results also showed the antagonistic substance had strong polar. The ammonium sulfate precipitation from A. brassicae fermentation had strong inhibition to the hypha growth of P. infestans, but its ethanol precipitation did not show inhibition to the hypha growth of P.infestans. That showed the effective antagonistic substances in the A. brassicae fermentation may be protein substances. The ammonium sulfate precipitation and ethanol precipitation from A. kikuchiana fermentation and its hypha's crude extracts did not show strong inhibition to the hypha growth of P.infestans. That showed the effective antagonistic substances in the A. kikuchiana fermentation and hypha were not protein substances.