Specialisation of Erysiphe quercicola on Rubber Tree and Murraya paniculata

Erysiphe quercicola is a plant pathogen causing powdery mildew on a wide range of woody plants, especially in tropical regions, including rubber tree ( Hevea brasiliensis ), which is an economically important tree species producing natural rubber. It is unknown whether specific genetic lines of E. quercicola , which are morphologically indistinguishable, are restricted to a limited subset of the host range. In this study, the causal agent of powdery mildew on Murraya paniculata (orange jasmine) from Hainan and Yunnan, China, was first identified using morphological characters and multilocus phylogenetic analyses. The results indicated that E. quercicola was the causal agent of powdery mildew on M. paniculata . Based on cross‐pathogenicity analysis, E. quercicola from M. paniculata could not infect rubber tree and the reciprocal test found that E. quercicola from rubber tree could not infect M. paniculata , confirming that host specificity occurs for E. quercicola between M. paniculata and rubber tree. To our knowledge, this is the first report of different host specificity within E. quercicola .