Erioglossum rubiginosum, a new alternative host of rubber tree powdery mildew Erysiphe quercicola

Erioglossum rubiginosum (synonym as Lepisanthes rubiginosa), is a shrub-like plant belonging to the family Sapindaceae. This species is a common undergrowth plant species in rubber tree plantations, which provide more than 90% of the total natural rubber production. Powdery mildew was found to occur seriously on E. rubiginosum during an investigation on powdery mildew of rubber tree caused by Erysiphe quercicola. In this study, leaves of E. rubiginosum with powdery mildew symptoms were collected and the pathogen was identified using morpho�logical and molecular analyses using the internal transcribed spacer (ITS) and 28 S rDNA regions. The results indicated that E. quercicola was the causal agent of E. rubiginosum powdery mildew. Based on cross-pathogenicity analysis, E. quercicola from E. rubiginosum and rubber tree could cause typical symptoms on each other, which confirmed that E. rubiginosum is an alternative host of rubber tree powdery mildew. To our knowledge, this is the first report of E. quercicola causing powdery mildew on E. rubiginosum. Whether E. rubiginosum can be one of the primary sources of the rubber tree powdery mildew epidemics needs future studies.