Abstract
The stem rot of Chrysanthemum zawadskii var. latilobum occurred in the landscape field of Sanggwan-myeon, Wanju-gun, Jeonbuk, Korea in September 2009. The typical symptoms of the disease were water-soaking and dark brown rot on the stem, wilting and blighting. Most infected plants died of the disease. White mycelial mats were spread over lesions and brown sclerotia were formed on stems and near soil surface. The sclerotia were spherical or irregular, 0.8-3.5 (mean 1.8) mm in size on potato dextrose agar, brown in color. The optimal temperature range of hyphal growth was $25-30^{\circ}C$ and the hyphal diameter was 4-9 ${\mu}m$. Clamp connections were observed in the hyphae of the fungus grown on potato dextrose agar. Pathogenicity of the casual organism was provided on C. zawadskii according to Koch's postulate. The fungus was identified as Sclerotium rolfsii on the basis of mycologiclal characteristics and pathogenicity test to host plants. This is the first report on the stem rot of C. zawadskii caused by S. rolfsii in Korea.
2009년 9월에 전북 완주군 상관면 조경포장에 재배중인 구절초의 줄기와 지제부위가 수침상으로 무르고 썩으면서 암갈색으로 시들어 말라 죽었다. 병반부와 지제부위의 토양 표면에 흰색의 균사가 자라고 갈색의 구형 또는 부정형의 균핵이 형성되었다. 균사의 생육적온은 $25{\sim}30^{\circ}C$이었으며, 균사의 폭은 4-9 ${\mu}m$이었고, 균핵의 크기는 0.8-3.5(평균 1.8) mm이었다. 균사특유의 clamp connection이 관찰되었다. 분리한 균은 구절초에 대한 실험결과 병원성이 인정되었다. 구절초에 발생한 병징과 분리균의 균학적 특징 및 병원성을 검정한 결과, 이 병을 Sclerotium rolfsii에 의한 구절초 흰비단병으로 명명하고자 한다.
