Collar Rot of Broad Bean (Vicia faba) Caused by Sclerotium rolfsii

Sclerotium rolfsii에 의한 잠두 흰비단병 발생

A destructive collar rot disease was found on broad bean (Vicia faba) in several farmer's field located in Changseon-myon, Namhae-gun, Gyeongsangnam-do in 2001. The typical symptoms of the disease were stem rot, crown rot, wilt or blight. Upper parts of the infected stems were mostly blighted and white mycelial mats were spread over lesions and the sclerotia were formed on the stems near soil line. The infection rates of the disease in the surveyed area were ranged from 28.6 to 42.8%. The sclerotia of the fungus readily formed in artificial media such as PDA at $30^{\circ}C$ and its shape was globoid or irregular and size was $1.0{\sim}3.7{\times}1.0{\sim}2.8\;mm\;(av.\;1.0{\sim}2.3\;mm)$ and was brown or dark brown in color. The optimum temperature for growth of the fungus was about $30^{\circ}C$. The typical clamp connections were found in the hypha of the fungus grown on PDA. On the basis of mycological characteristics and pathogenecity test on host plants, the fungus was identified as Sclerotium rolfsii. This is the first report on the collar rot of broad bean caused by Sclerotium rolfsii in Korea.

2001년 경상남도 남해군 창선면 잠두 재배포장에서 줄기가 부패하고 주위에 흰곰팡이가 발생하는 병이 관찰되었다. 이 병의 병징은 지제부가 암갈색으로 변하고 그 위에 흰색의 곰팡이가 솜털처럼 밀생하고, 병반 부위에 갈색의 둥근 균핵을 많이 형성하며 지제부 부근의 토양 표면에도 형성되었다. 병원균은 PDA 배지 상에서 $30^{\circ}C$에서 가장 잘 자랐으며 균사생장 중에 특유의 clamp connection이 관찰되었다. PDA 배지에서 갈색 또는 암갈색을 띤 구형 또는 부정형의 많은 균핵을 형성하였으며, 균핵의 크기는 $1.0{\sim}3.7{\times}1.0{\sim}2.8\;mm$(평균 $1.0{\sim}2.3\;mm$)였다. 병원균의 특징과 병원성을 검정한 결과 이 병을 Sclerotium rolfsii에 의한 잠두 흰비단병으로 명명하고자 한다.