Occurrence of Fruit Rot of Watermelon (Citrullus lanatus) Caused by Sclerotium rolfsii

The fruit rot of watermelon (Citrullus lanatus) occurred sporadically in the farmers field at Chojeondong, Jinju city, Korea, in 2007. The typical symptom was water-soaked, brown on the fruit, and than infected fruits were mostly rotted. White mycelial mats were spread over lesions, and then sclerotia were formed on fruit and near soil line. The sclerotia were globoid in shape, $1{\sim}3\;mm$ in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$ and the hyphal width was $4{\sim}8{\mu}m$. The typical clamp connections were observed in the hyphae of the fungus. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii. This is the first report on the fruit rot of watermelon by S. rolfsii in Korea.

Sclerotium rolfsii에 의한 수박 흰비단병 발생

2007년 5월 상순 진주시 초전동 비닐하우스 수박 재배 포장에서 수박 흰비단병이 발생되었다. 병정은 과실 아랫 부분이 수침상으로 물러지고 부패되면서 병반부와 토양 표면에 흰색의 곰팡이가 솜털모양으로 생기고 갈색의 둥근 균핵을 많이 형성하였다. 균핵의 크기는 $1{\sim}3\;mm$이며 균사의 폭은 $4{\sim}8{\mu}m$로서 균사생육과 균핵형성 적온은 $30^{\circ}C$이었다. 균사특유의 clamp connection이 관찰되었다. 수박에서 발생한 병징과 병원균의 균학적 특징 및 병원성을 검정한 결과, 이 병을 Sclerotium rolfsii에 의한 수박 흰비단병으로 명명하고자 제안한다.