Stem Rot of Obedient plant (Physostegia virginiana) Caused by Sclerotium rolfsii

In May 2002, a destructive stem rot of Obedient plant (Physostegia virginiana) occurred sporadically in an exhibition farm of Hamyang-gun, Gyeongsangnam-do Agricultural Research and Extension Services, Korea. The typical symptoms of the disease were stem rot, crown rot, wilt or blight. Upper parts of the infected stems were mostly blighted. White mycelial mats were spread over lesions and the sclerotia were formed on the stems near soil line. The sclerotia was globoid or irregular in shape, 1${\sim}$3 mm in size, and brown in color. The optimum temperature for fungal growth was about $30^{\circ}C$. The typical clamp connections were observed in the hyphae of the fungus grown on PDA, and hyphal diameter was 3.6${\sim}$9.4 ${\mu}m$. On the basis of mycological characteristics and test of pathogenecity to host plants, the fungus was identified as Sclerotium rolfsii. This is the first report on the stem rot of Physostegia virginiana caused by Sclerotium rolfsii in Korea.

Sclerotium rolfsii에 의한 꽃범의꼬리 흰비단병 발생

2002년 경상남도농업기술원 함양약초시험 포장에 재배중인 꽃범의꼬리에서 이상증상이 발생하였다. 병징은 지제부의 줄기가 수침상으로 물러지고 부패하면서 암갈색으로 변하고 그 위에 흰색의 곰팡이가 솜털처럼 생기고, 병반 부위와 토양 표면에 갈색의 둥근 균핵이 많이 형성된다. 병원균의 균사생장 및 균핵형성은 PDA배지에 배양시 $30^{\circ}C$에서 가장 양호하였다. 균핵은 갈색 또는 암갈색으로 크기는 1${\sim}$3 mm이었다. 균사 특유의 clamp connection이 관찰되었고 균사 폭은 3.6${\sim}$9.4 ${\mu}m$이었다. 본 병원균을 Sclerotium rolfsii로 동정하였으며 꽃범의꼬리 흰비단병으로 명명할 것을 제안한다.