Lasiodiplodia theobromae引起之馬拉巴栗編辮苗黑腐病

2011-2013年間，在馬拉巴栗的編辮場、集貨場及田間病害調查時發現編辮苗經常發生根部軟化、黑褐色腐敗與纖維化，莖部黃化、枯死，最後導致苗木失編或死亡情形。小編辮苗在編辮後7-14天內即會發病，發病率嚴重時可達100%。而移植於田間的中、大編辮苗在移植後0-3個月內發病，發病率可高達60%以上。編辮苗收穫後，送至集貨場的植株亦會由傷口開始發病，造成貨品根部與莖部產生黑色腐敗，使貨品喪失外銷價值。經病原菌分離與病原菌形態鑑定，輔以ITS序列比對，且依柯霍氏法則（Koch's postulates）完成病原性測定，病原菌鑑定為Lasiodiplodi atheobromae（Pat.）Griff. & Maubl.，造成之病害稱為馬拉巴栗編辮苗黑腐病，英名為black rot of braided seedlings of Malabar chestnut。病原菌在馬鈴薯葡萄糖瓊脂（PDA）培養基上，菌落形態呈現濃密的灰黑或暗黑色，並會有黑色柄子殼（pycnidia）形成，其大小介於0.7-3.4 mm之間，平均1.9 mm。成熟的柄子殼上有孔口（ostioles），大量成熟的褐色分生孢子（conidia）便由孔口擠壓釋放而出。未成熟的分生孢子透明、無隔膜、近卵形到長橢圓形、基部鈍狀。成熟的分生孢子為橄欖型或短桿狀、雙室、黑褐色、有縱向條紋，大小介於11.4-17.5×21.5-31.1 μm之間，平均14.5×25.8 μm。本病原菌菌絲在8-39℃下皆可生長，最適生長溫度為28℃，生長速率介於19.5-29 mm/day。供試植株之最適發病溫度為24-32℃。L. theobromae危害馬拉巴栗為世界首次報導。

關鍵字

馬拉巴栗；傷口；編辮苗黑腐病

並列摘要

During field survey from 2011 to 2013, many diseased braided seedlings of Malabar chestnut were found to show root rot and stem yellowing and wilted, which finally caused the death of the whole plant. Longitudinal sections of the diseased root tissues showed internal dark brown discoloration. For the young braided seedlings (3- to 6-month-old), the disease symptoms appeared 7-14 days after braiding, and the disease incidence could reach as high as 100%. The disease incidence was up to 60% for larger braided seedlings (1- to 2-year-old) after transplanting into the field for 0-3 months. After harvesting, similar disease symptoms also appeared on the wounded part of the harvested plants. Such commodities would lose their values in export markets. Several fungi and oomycetes were isolated from the diseased samples, but only one fungus caused black rot on the inoculated seedlings. Therefore, the fungus isolate F211251 was chosen to conduct the pathogenicity test for completing Koch's postulates. According to the morphological characteristics and the molecular sequence of internal transcribed spacer (ITS) of ribosomal DNA, the pathogen was identified as Lasiodiplodia theobromae (Pat.) Griff. & Maubl. The disease was named as braided seedling black rot of Malabar chestnut. The colony of the pathogen on PDA medium was grey to black, fluffy, with abundant aerial mycelium. It formed numerous black pycnidia [0.7-(1.9)-3.4 mm] on 2% water agar amended with host tissues. Young conidia were unicellular, hyaline, sub-ovoid to oblong. Mature conidia become 1-septated, brown to dark brown, thick-walled, base truncate, often longitudinally striate, and its size was 11.4-(14.5)-17.5×21.5-(25.8)-31.1 μm. The optimum temperatures for mycelial growth and disease development were 28℃ and 24-32℃, respectively. The disease of braided seedling black rot of Malabar chestnut caused by L. theobromae has not been reported in any other countries prior to this report.

並列關鍵字

Malabar chestnut ； Lasiodiplodia theobromae ； wounded treatment ； braided seedling black rot

國際替代計量

Lasiodiplodia theobromae引起之馬拉巴栗編辮苗黑腐病

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