紅龍果果腐及仙人掌莖腐病

Abstract

於西元2003-2004年間，連續調查桃園及彰化兩地進口之觀賞仙人掌與國內生產的紅龍果果實，發現皆受Bipolaris sp.的感染。故將觀賞用仙人掌山吹(Echinopsis chamecereus f. lutea)的莖部分離株(DC-06)及紅龍果(Hylocereus undatus)果實分離株(DC-07)分別接種於紅龍果果實與山吹莖部，兩菌株皆可造成紅龍果果皮呈現淡褐色壞疽病斑，及山吹莖部形成紅褐色至黑色壞疽病斑。兩菌株培養於馬鈴薯葡萄糖瓊脂上，病原菌分生孢子柄表面平滑，直立或彎曲，基部膨大，呈黃褐色，大小為48-100×4-6μm，單生或簇生，於寄主植物病斑上常呈簇狀生長；分生孢子柄頂端常呈不規則裂瓣(lobed)或簡單膨大或膝狀彎曲(geniculate)；分生孢子平直，紡錘形至倒棍棒狀，大小為15-64×6-14μm，淡褐色至黃褐色，2-4個隔膜，孢痕(hilum)輕微突出；分生孢子發芽時，多為兩極生(bipolar)，且接近孢痕之發芽管為半向軸的(semiaxial)生長方向。進一步接種試驗顯示，其穩定發病之接種濃度為10^4 spores/ml以上；病原菌菌絲生長及病勢發展之適合溫度皆為25-35℃之間；寄主範圍的測定結果顯示，病原菌僅感染仙人掌科植物，其餘13種非仙人掌科植物皆無病徵產生。依據上述病原菌形態及其寄主範圍，鑑定病原菌為Bipolaris cactivora，為台灣首次記錄。 Two isolates obtained from decayed imported yellow peanut cactus (Echinopsis chamecereus f. lutea) (DC-06) and domestic pitaya (Hylocereus undatus) fruit (DC-07) were inoculated on health stern of yellow peanut cactus and pitaya fruit to confirm their pathogenicity. The inoculated yellow peanut cactus appeared red-brown to black stern rot and pitaya fruit showed light brown lesions. Both of them were similar to those of natural infection and identical fungi were reisolated from diseased tissues. The conidiophores of the pathogens are smooth, straight or flexuous, swollen at the bases, light brown to yellow brown, 48-100×4-6μm, fascicled or single on potato dextrose agar and caespitose on host plants. The tips of conidiophores are usually irregularly lobed, simply swollen, or geniculate. The conidia are straight, fusiform to obclavate, 15-64×6-14μm, yellow brown, 2-4 septa, and with a truncate hilum slightly protruding. Most conidia are bipolar germination and the growth of basal germ tube is semiaxial. In host range tests, the pathogens can infect the species in Cactaceae including Astrophytum asterias, Cereus jamacaru, Echinocactus grusonii, Echinocereus chloranthus, Echinopsis calochlroa, Espostoa melanostele, and Hylocereus sp.(with red pulp). According to fungal morphology and their host range, the pathogens were identified as Bipolaris cactivora (Petr.) Alcorn. The suitable temperatures for disease development and for mycelial growth are 25-35℃. This is the first report for both the diseases and their pathogens in Taiwan.