Abstract: Brown blotch disease caused by Pseudomonas tolaasii is an important mushroom disease. It can cause serious yield and quality loss. Early detection and monitoring of the pathogen is crucial step for disease control. A real-time fluorescent quantitative PCR by using specificity primer（Pt-1A）/（Pt-1D1）and enrichment method was developed to detect the bacterial pathogens of P. tolaasii. The method was uesd to analyze the bacterial population dynamic change of P. tolaasii on the Pleurotus ostreatus sporocarp surface. Our results showed that the detection range of this was from 10² to 10⁹ cfu ? mL^-1，and the sensitivity with enrichment step can reach about 100-fold higher than that without enrichment step. We conclude that the real-time quantitative PCR with the enrichment method can be used to detect P. tolaasii at the early stage of infection，and can provide technical support for the mushroom bacterial epidemic surveillance and early prevention of the disease.

Key words: Pleurotus ostreatus, Pseudomonas tolaasii, real-time fluorescent quantitative PCR