Tian Yan-li;Zhao Yu-qiang;Chen Bao-hui;Chen Shuo;Zeng Rong;Hu Bai-shi;Li Xiang

Nanjing Agr Univ, Coll Plant Protect, Minist Educ, Nanjing 210095, Peoples R China;Jiangsu Prov & Chinese Acad Sci, Inst Bot, Nanjing Bot Garden Mem Sun Yat Sen, Jiangsu Key Lab Res & Utilizat Plant Resources, Nanjing 210014, Peoples R China;Nanjing Agr Univ, Key Lab Integrated Management Crop Dis & Pests, Minist Educ, Nanjing 210095, Peoples R China;Canadian Food Inspect Agcy, Charlottetown Lab, Charlottetown, PE C1A 5T1, Canada

molecular assay;pear bleeding canker;detection

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 mu L-1 DNA and 1x 10(3) 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.