Occurrence, Pathogen Characterization and Control of Phomopsis destruens Causing Foot Rot of Sweet Potato

Abstract

由 Phomopsis destruens (Harter) Boerema 引起之甘藷基腐病為近年來嚴重影響國內甘藷生產之重要限制因子，本病害不僅危害鮮藷用之「台農57 號」及「台農66 號」，亦危害葉菜用甘藷「台農71 號」，顯示台灣主要栽培的甘藷品種皆不具抗病性。其病徵為在甘藷主藤蔓靠土表的莖基部造成黑褐色乾枯，使受害植株之地上部生長勢衰弱、葉片黃化枯萎、新葉變小，同時由於乾枯部位緊鄰塊根生長處，因此塊根發育亦會受阻，造成塊根受害部位表面呈淡褐色濕腐，進而導致產量嚴重損失及儲藏時之病害問題。本病原菌在甘藷病株藤蔓表面佈滿大小不一、黑色、凸起狀之柄子器，內含兩型分生孢子。本病害之主要感染源為罹病種苗，因此清潔種苗來源為防治本病害之重要策略；於曾發病之甘藷田進行淹水處理2 週以上或與水稻輪作，可減少病藷及病殘體上之菌體，避免作為下一期作之感染源；另外藥劑防治試驗結果顯示，貝芬菲克利及腐絕均具有顯著防治本病害發生之效果。綜合上述本病害之防治策略為1.選用經認證之健康種苗進行栽植。2.田間栽培時期及採收前若發現發病植株應整株含地下部進行清除，並移出田間，以減少田間感染源。3.發病區建議於種植前進行淹水或水稻及非寄主作物輪作，以降低田間感染源密度。 Foot rot disease is a major limiting factor of sweet potato production in recent years. The disease was harmful to commercial root-used varieties of sweet potato, TN57 and TN66, as well as vegetable-used variety, TN71. It suggested that the majority of sweet potato cultivars in Taiwan were not resistant to this disease. The symptoms of this disease included yellowing of leaves, necrotic lesions on vine, and wilting of the sweet potato plants. The pathogen might grow from cankers on the vines down into storage roots, having brown wet rot lesions on the skin of storage root, and caused to severe yield loss and storage disease problems. The fungus generated two types of conidia from stromataic pycnidia on infected vines. The disease seedling was a major inoculum source. Therefore, good quality of seedlings would be an important factor to control the foot rot of sweet potato in the field. It was recommended that the field with the foot root disease should be rotated with rice annually or being flooded for more than 2 wk after harvesting season, and it could eradicate the pathogen as well as avoid the infection of foot rot disease next season. In the chemical control, the result showed that Carbendazim + Hexaconazole and Thiabendazole were effectively inhibited mycelial growth. From all the experimental data, possible integrated control strategies to the disease include (1) cultivating certified healthy seedling, (2) eliminating all disease-infected plants in the field, and (3) adopting flooding treatment or rotation of rice and non-host crops prior to planting season to reduce the pathogen density of the field