Mixed Fermentation of Two Antagonistic Fungi Against Phytophthora infestans and Stability of Anti-fungi Substances

To obtain the stable biocontrol preparation for controlling potato late blight,the feasibility of mixed fermentation for antagonistic fungi Alternaria alternate LH-03 and A.brassicae BH-09 against growth of Phytophthora infestans and the fermentation conditions were investigated,and then the stability of antagonistic substance in fermentation filter was tested in this experiment.The results showed that there were no antagonistic effects for two antagonistic fungi.The mixed fermentation could increase the anti-fungi activity to P.infestans.The optimized conditions for mixed fermentation were pH 6.29,25 ℃,standing culture for 4 days in the dark.Inhibition rate of fermentation liquid at optimized condition was up to 92.15% and stronger than that of two fungi fermentation independently.The fermentation product at optimized condition after treatment with different temperature and pH,its anti-fungi activity remained basically unchanged or declined slightly,especially for the inhibitory rate could reach 66.78% with high temperature treatment at 121 ℃,and 68.67% with pH 2 treatment,respectively.It is indicated that the fermentation product at optimized condition had a great potential in control potato late blight in future since it displayed strong thermal stability and well resistance to superacid and strong alkali.