台灣山藥根瘤及乾腐病之病原線蟲鑑定與防治

The identification and of the causal nematodes of Yam root-knot and dry rot diseases

"嘉義縣中埔鄉與台南縣左鎮鄉山藥發生病變，罹病山藥薯塊上出現瘤狀突起和乾腐裂陷之病徵。觀察取自山藥薯塊中之根瘤線蟲母蟲之陰門膜紋型態與Meloidogyne incognita Chitwood，1949相符；二齡幼蟲型態測量之尾長介於46.3-52.5μm，尾部透明區介於10.0 -13.1μm，鑑定此線蟲為南方根瘤線蟲M. incognita。乾腐病徵裂陷處橫切後，於切面可發現薯塊外緣褐化乾腐，所分離的線蟲雌蟲之陰門位於蟲體後端三分之一處，口針明顯、基部結球大，口唇部和身體稍微分離，具2個體環、4條側線，尾部呈圓柱狀，尾端有鋸齒狀或平切狀，與南方根腐線Pratylenchus coffeae Filipjev and Stekhoven, 1941之型態相符。篩選18個本省常見之山藥品系，結果顯示對本地的M. incognita及P. coffeae並無抗性或耐性。研究以三種方式處理感染線蟲的薯塊，發現化學藥劑浸種或是漠化甲烷燻蒸罹根瘤病及乾腐病之山藥薯塊，無法完全除滅山藥薯塊中之線蟲。溫湯浸種的處理則可以完全除滅山藥種薯內的線蟲;以50°C浸種90分鐘可以殺死根瘤線蟲並且其卵塊也無侵染番茄的能力。另以較低的溫度，如48°C處理90分鐘，或49°C處理30分鐘，皆可有效防除根腐線蟲，且不影響薯塊之發芽率。"

"The common yam planted in Zhongpu township, Chiayi County and Zuozhen township, Tainan county were infected by plant parasitic nematodes. The diseased yam tuber had either galling or dry rot symptom on the surface. The root-knot females recovered from the galling yam tuber were processed for the perineal pattern, and found to be the same as Meloidogyne incognita Chitwood, 1949. The J_2 had the tail length between 46.3-552.5μm and the tail hayline region 10.0-13.1μm. According to these data, the nematode was identified as M. incognita. Cross-dissecting the dry rot diseased yam could found the tissue under the epiderma was brown and dried. The female nematode isolated from these tubers had pronounced stylet and stylet knobs. The lip region was slightly off-set with 2 body annuals. The lateral region had 4 incisures, tail conical shaped with either saw-like or blunt tail end. These morphomatrical data was consistent with Pratylenchus coffeae Filipjev and Stekhoven, 1941. Screening of the 18 common yam cultivars that planted with higher frequency in Taiwan found no resistance or tolerance to either M incognita or P. coffeae. Three pre-planting tuber treatments were tested in this study, and the results found that nematicides soakage or methyl bromide fumigation could not effectively kill these 2 nematodes parasited in the common yam tubers. However, warm water bath could kill all root-knot nematodes at 50°C, treating for 90 mins, and the egg masses recovered from the treated tuber could not infect water spinach later. P coffeae could be killed at the lower temperature; treating the tuber at 48°C for 90 mins or 49°C for 30 mins could ensure the death of the nematode."