Abstract: Considering the Pichia pastoris G5,a biocontrol strain isolated from red grape in Xinjiang and using Botrytis cinerea as target strain,we studied the effects of G5 on the spore of B. cinerea and the activities of five enzymes in the red grape fruit,and primarily explored the antagonistic mechanisms of G5 against B. cinerea by in vitro and in vivo experiment. Results showed that the G5 obviously inhibited the germination of B. cinerea spores and the growth of mycelium,and the rate of inhibiting mycelium maximally reached 80.20% and the rate of inhibiting spore germination was 86.89%. Nutritional competition existed between the G5 and B. cinerea. In the course of antagonism,the heavy parasitism phenomenon occurred. Experiment sindicated that G5 itself did not secrete antimicrobial substances. In addition,the strain induced and significantly increased the enzymes’ activities in fruit,such as peroxidase,polyphenol oxidase,phenylalanine ammonia lyase,chitinase,and β-1,3-glucanase. The inhibition mechanisms of G5 to B. cinerea include nutrition competition and inducible resistance；whether or not there is heavy parasitism needs to be further validated.

Key words: Botrytis cinerea, biological control, Pichia pastoris G5, antagonistic mechanism