Neottiosporina cylindrica造成之輪傘莎草褐斑病

Brown spot of Cyperus involucratus caused by Neottiosporina cylindrica

2017至2018年間於臺灣中部彰化及苗栗地區觀察到輪傘莎草（Cyperus involucratus）葉片具有褐色病斑，病斑中央組織呈現破裂、白化現象，嚴重時葉片枯黃、莖頂萎凋斷裂，採集罹病葉片進行組織分離，並以科霍氏法則確認各分離株皆具有病原性。病原菌可於含有莎草組織的PDA培養基中產生黑色柄子殼（pycnidia），柄子殼內形成無色、單隔、頂端及基部細胞不對稱之柄孢子（pycnidiospores），柄孢子為圓筒狀、頂端具傘型附著物（umbraculiform appendages）。以ITS及LSU基因進行親緣演化樹分析，顯示病原菌屬於Neottiosporina屬，再根據形態特徵鑑定病原為Neottiosporina cylindrica B. Sutton & Alcorn.。進一步試驗環境溫度對病原菌及病害發展的影響，菌絲及柄孢子在16~32℃皆可生長與發芽，並以28℃為最適溫度，而病斑之發展則以20℃下病徵最顯著。對其他寄主之病原性測試顯示，病原菌具有感染土香（Cyperus rotundus）、短葉水蜈蚣（Kyllinga brevifolia）及水稻臺農67號的潛力，但對其他測試之糧食作物（包含水稻台南11號）皆不具病原性。N. cylindrica引起輪傘莎草褐斑病為各國未曾紀錄之新病害，亦為臺灣Neottiosporina屬真菌之首次記錄。

"In 2017 and 2018, brown spots of umbrella flat sedge (Cyperus involucratus Rottb.) were observed in both Chenghua and Miaoli counties, central Taiwan. Brown spots on leaves are necrotic lesion with cracked and white epidermis in center. Severe damages caused chlorotic and dry-out leaves, and even collapsed entire canopy. Pathogenicity of fungal isolates that were isolated from diseased leaves was verified by the Koch's postulates. Pathogens formed numerous black pycnidia on pieces of sterilized sedges leaf laid on PDA. Pycnidiospores were asymmetrically 1-eusptate, cylindrical, hyaline, with apical appendages mostly in umbraculiform. Phylogenetic analysis based on concatenated sequences of ITS and LSU revealed that the isolates belonged to the genus of Neottiosporina. According to the morphological characteristics, the isolates were identified as Neottiosporina cylindrica B. Sutton & Alcorn. The effects of environmental temperatures on the pathogens and the disease were further assessed. The optimum temperatures for mycelial growth and pycnidiospore germination were 28℃, while the optimum temperature for disease development was 20℃. Host range assays indicated that the pathogens were potentially pathogenic to green kyllinga (Kyllinga brevifolia), purple nutsedge (Cyperus rotundus) and rice Tainung No. 67 (Oryza sativa L. cv. Tainung No.67), but not to tested other staple crops (including O. sativa L.cv. Tainan 11). To our knowledge, this is the first report of the fungus in Taiwan and of the brown spot disease on C. involucratus worldwide."