Real-time PCR assay for detection of Dickeya fangzhongdai causing bleeding canker of pear disease in China

Abstract

Bleeding canker, caused by Dickeya fangzhongdai, is a devastating disease of pear in China. The bacterium causes cankers, branch die-back, and eventually kills pear trees. The typical sign of bleeding canker infection is a rusty-brown bacterial ooze that exudes down from cankers onto branches or trunks. However, early symptoms and signs are inconspicuous, which makes effective disease management difficult. Detection and identification of D. fangzhongdai are time-consuming and difficult because no rapid method exists to date. In this study, a TaqMan real-time PCR assay was developed for D. fangzhongdai based on an elongation factor G (fusA) gene. The real-time PCR assay detected 0.2 pg μL−1 DNA and 1×103 CFU mL−1 of D. fangzhongdai. Based on this assay, bleeding canker on asymptomatic pear trees can be diagnosed as early as 5 days after infection. The real-time PCR assay can facilitate disease management by providing early and accurate diagnosis of the bleeding canker disease of pear.