Abstract: This study is aimed at defining the induced resistance，hypovirulent pathogenicity and the genetic，induced concentration and interval of induction. Hypovirulent pathogenicity of the strain could be inherited to next five generation stably. The efficiency of induced systemic resistance against brown blotch disease by the five generations was 67.2%，66.3%，69.1%，68.6% and 65.0%，respectively. To summarize，the study provided a theoretical basis for application of the hypovirulent strain as a biocontrol agent to control the P. ostreatus brown blotch disease. stability of the hypovirulent strain JPG250303 in Pleurotus ostreatus. The strain was identified as Pseudomonas tolaasii combining morphology and molecular biological methods. Good induced resistance effect of the hypovirulent strain was proved by studies of induced resistance

Key words: Pleurotus ostreatus, Pseudomonas tolaasii, hypovirulent strain, induced resistance