Occurrence of Stem Rot of Petunia hybrida Caused by Sclerotium rolfsii

From 2006 to 2008, the stem rot of Petunia hybrida Vilm. caused by Sclerotium rolfsii occurred sporadically at Jinju city in Gyeongsangnam-do. The typical symptom is water-soaking, brown on the stem and rotting, wilting and blighting. The infected plants were mostly died. White mycelial mats were spread over lesions, and then sclerotia were formed on stem 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 was at $30^{\circ}C$ on PDA and the hyphal width ranged from 4 to $8{\mu}m$. The typical clamp connections were observed in the hyphae of the fungus. On the basis of mycological characteristics and pathogenicity to P. hybrida, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the stem rot of P. hybrida caused by S. rolfsii in Korea.

Sclerotium rolfsii에 의한 페튜니아흰비단병 발생

2006년에서 2008년까지 진주에서 재배중인 페튜니아에서 병이 발생하였다. 병징은 줄기와 잎이 수침상으로 물러지고 썩으면서 갈색으로 변하며 시들어 말라 죽었다. 줄기, 지제부 및 토양 표면에 솜털모양의 흰색 균사체가 생기고 $1{\sim}3\;mm$ 크기의 둥근 갈색 균핵을 많이 형성하였다. PDA배지 상에서 병원균의 균사 폭은 $4{\sim}8\;{\mu}m$이며 clamp connection이 형성되었고 균사생육과 균핵형성 적온은 $30^{\circ}C$이었다. 페튜니아에서 발생한 병징과 병원균의 균학적 특징 및 병원성을 기초로 본 병을 Sclerotium rolfsii Saccardo에 의한 페튜니아 흰비단병으로 명명하고자 제안한다.