Abstract: The antifungal activities of 95% ethanol and hexane extracts of tobacco against Valsa mali and other 10 plant pathogens were studied.The antimicrobialcomponents of tobacco extracts were measured by HPLC and GC-MS.Results showed that the 2 investigated solvent extracts both had inhibitory effects on all the tested plant pathogens,among which V.mali received strongest inhibition,and hexane extracts had stronger antifungal activity than 95% ethanol extract at the same concentration level.According to the antifungal characteristics of different extracts of tobacco and several pure substances,it was speculated that cembranoids were the main antifungal substance.

Key words: tobacco extracts, plant pathogenic cembranoids fungi, antifungal activity, cembranoids