Occurrence of Downy Mildew on Watermelon (Citrullus Lanatus) Caused by seudoperonospora cubensis on Seedling Nursery in Korea

Kwon, Jin Hyeuk; Park, Chang Seuk

Research in Plant Disease 2006;12(2):125-128.
Published online August 30, 2006.

육묘상에서 Pseudoperonospora cubensis에 의한 수박 노균병 발생

권진혁, 박창석

Occurrence of Downy Mildew on Watermelon (Citrullus Lanatus) Caused by seudoperonospora cubensis on Seedling Nursery in Korea

Jin Hyeuk Kwon, Chang Seuk Park

Abstract

Downy mildew caused by Pseudoperonospora cubensis (Berkeley & Curtis) occurred on the cotyledon of gourd (Lagenaria leucantha cv. Sambokkkul) and scion of watermelon (cv. FR couple) in commercial nursery around Jinju city, Gyeongnam province in Korea in 2005 and 2006. The disease symptoms usually started with water-soaking lesions on cotyledon and then the infected leaves became withered and eventually died. The sporangia of the pathogen were one-celled, ovoid to ellipsoid in shape, pale grayish in color, and 20~32 × 14~18 μm in size. Sporangiophores were errect, branched, and 140~380 × 4~8 μm in size. Pathogenicity of the causal organism was proved according to artificial inoculations. Although the virulence of the causal fungus on the host plants was not strong, it produced typical symptoms. The causal organism was identified as Pseudoperonospora cubensis (Berkeley & Curtis) based on the mycological characteristics of the fungus and pathogenicity. This is the first report on downy mildew of watermelon caused by P. cubensis in Korea.

Key Words: Downy mildew, Lagenaria Leucantha, Pseudoperonospora cubensis, Watermelon