• 作者： 陳主得
• 作者服務機構： 臺灣糖業研究所
• 中文摘要： 由不完全菌Periconia manihoticola引起之樹薯葉斑病係屬樹薯新病害。該病原菌除樹薯外，尚可侵害巴西橡樹(Hevea brasiliensis)。本菌產生暗褐色具突起之球形分生胞子為特徵，胞子大小不一，直徑22～43μm，長於最頂端者最大。樹薯葉片於胞子接種24～36小時後，出現小圓形褐色斑點，外圍並具黃暈。以後病斑漸次擴大，直徑2～4 mm，具深褐色外緣，內部則為淺褐色，組織壞疽。有時數個斑點連合，成不整形之病斑。P. manihoticola於22℃生長最佳，分生胞子於18℃及22℃之發芽率亦較30℃良好，顯示本菌偏好低溫。此種特性與本病常於海拔較高地區發生可能有關。
• 英文摘要： A previously undescribed leafspot diseasecaused by Periconia manihoticola was found oncassava (Manihot esculenta) at Pu-Li, Taiwan in1975. P. manihoticola sporulated well on PSAand V-8 juice agar, producing dark brown,globose and verrucose conidia which variedwidely in size, from 22μm to 43μm in diameter.Small circular brown spots with yellow halosdeveloped on inoculated leaves 24-36 hrs afterinoculation. The spots enlarged to 2-4 mm witha dark brown border, and the center of the spotgradually turned to light brown in color. Allof the tested cassava clones including Wu-Chi,I-Chi-Hsiang and Pai-Fen were susceptible. Theoptimum temperature for mycelial growth of P.manihoticola was 22℃. Spores germinated betterat 18° and 22℃ than those at 30℃. Theseevidences indicated that the fungus tended togrow and survive at lower temperature. Thischaracteristics might be in accordance with thefact that Periconia leaf spot of cassava alwaysoccurred on the hill sides at the higher elevation.
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