Occurrence of Sclerotium Rot of Cucumber Caused by Sclerotium rolfsii

Jin-Hyeuk Kwon; Sang-Dae Lee; Okryun Choi; Shun-Shan Shen; Hong-Sik Shim

Occurrence of Sclerotium Rot of Cucumber Caused by Sclerotium rolfsii

2015

Jin-Hyeuk Kwon | Sang-Dae Lee | Okryun Choi | Shun-Shan Shen | Hong-Sik Shim

Sclerotium rot of cucumber (Cucumis sativus L.) occurred at the experimental field of Gyeongsangnam-do Agricultural Research and Extension Services in July 2012. The typical symptoms included wilt, rot, and water-soaking on stems and fruits and severely infected plants eventually died. White mycelial mats spread over lesions, and then sclerotia were formed on fruit and near soil line. The sclerotia were globoid in shape, white to brown in color and 1−3 mm in size and the hyphal width was 4−8 μm. The optimum temperature for mycelial growth and sclerotia formation on PDA was 30oC. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. For further identification, the complete internal transcribed spacer (ITS) rDNA region was amplified and sequenced. On the basis of mycological characteristics, ITS rDNA region comparison, and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of sclerotium rot on cucumber caused by S. rolfsii in Korea.

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