Sooty Leaf Blight of Dendrobium sp. Caused by Pseudocercospora dendrobii

Pseudocercospora dendrobii에 의한 덴드로비움 검은잎마름병

Sooty leaf blight was found on Dendrobium sp. in several farmers' fields located in Namji-eup, Changnyeong-gun, Gyeongnam province, Korea in 2001. Symptoms of the disease appeared on leaves. Sooty leaf spots were started with amphigenous, subeircular to irregular spots, with light grayish brown to black color with definite margin lines on the upper surface of leaves. Infected leaves became defoliated and whole plants eventually were died. The infection rates of the disease in the surveyed area reached up to 64.8%, in the early September. Conidiophores of the causal fungus were dark grayish brown in color, densely fasciculate, straight, curved to sinuous, branched, $5{\sim}10$ septate and $63{\sim}164{\times}3.2{\sim}4.9{\mu}m$ in size. Conidia were pale to olivaceous in color, obclavatecylindric, straight to slightly curved in shape, $1{\sim}5$ septate and $46{\sim}98{\times}3.2{\sim}3.9{\mu}m$ in size. The optimum temperature for mycelial growth of the fungus was $25^{\circ}C$. The fungus was identified as Pseudocercospora dendrobii on the basis of its mycological characteristics. This is the first report on sooty leaf light of Dendrobium sp. caused by Pseudocercospora dendrobii in Korea.

2001년 경상남도 창녕군 남지읍 덴드로비움 재배포장에서 잎에 검은 잎마름 증상이 심하게 발생하였다. 병징은 아래 잎에 원형 또는 부정형의 점무늬가 생기며 표면은 옅은 갈색의 작은 함몰된 병반이 차차 증가하여 검게 변하면서 썩고 나중에 회색을 띤 검은색으로 말라죽으면서 낙엽이 된다. 조사한 포장에서 발생율은 64.8%이었다. 균사의 색깔은 짙은 올리브색이고, 분생자병은 옅은 회갈색을 띠며 $5{\sim}10$개의 격벽을 가지고 분지하며 끝 부분이 가늘고 둔하다. 크기는 $63{\sim}164{\times}3.2{\sim}4.9{\mu}m$이었다. 분생포자는 옅은 올리브색이며 가늘고 긴 곤봉모양이며 곧거나 약간 굽으며 $1{\sim}5$개 격벽을 가지며, 크기는 $46{\sim}98{\times}3.2{\sim}3.9{\mu}m$이었다. 균사 생육적온은 $20^{\circ}C$이었다. 이 병원균의 병징 및 균학적 특징, 병원성을 검정한 결과, P. dendrobii에 의한 덴드로비움 검은잎마름병으로 명명하고자 제안한다.