First report of powdery mildew caused by Erysiphe alphitoides on Japanese snailseed (Cocculus trilobus) in Korea.

Abstract

Japanese snailseed (Cocculus trilobus [C. orbiculatus]) has been known as a medicinal herb to treat dieresis, rheumatoid arthritis, and dropsy. In September 2011, severe powdery signs were found on several Japanese snailseed plants near Andong, Korea. Diseased leaves showed chlorotic or necrotic lesions, along with leaf distortion and senescence. Diseased leaves were associated with a fungus that resulted in what appeared to be white colonies, predominately associated with the upper leaf surfaces, and rarely on the lower surfaces. The colonies increased in size and coalesced, subsequently covering the entire surface. Based on morphological characteristics, sequence analysis of the rDNA internal transcribed spacer region and pathogenicity tests, the fungus was identified as E. alphitoides. This is thought to be the first report of the presence of E. alphitoides on Japanese snailseed in Korea. This fungus has been reported in association with numerous oak (Quercus spp.) species in Korea, showing that it may be a potential source of inoculum in Japanese snailseed.