台灣馬鈴薯與番茄晚疫病之發生現況與探討

Current status of potato and tomato late blight in Taiwan

"晚疫病是國際間馬鈴薯及番茄的重要病害，由Phytophthora infestans引起，經常造成重大的經濟損失。台灣自1908年即有晚疫病之記載，但病害在早年一直不嚴重，僅發生於夏秋季高山地區與冬春季濕冷之東北部，當時的菌系為基因型US-1（舊菌系，A1配對型）。1997年12月在台中后里地區爆發嚴重之馬鈴薯與番茄晚疫病後，兩個月內病害遍及全台，並導致馬鈴薯主產區由台中后里南移至雲林斗南地區，目前已經證實病害發生係因強毒性US-11基因型新菌系入侵之結果，該菌系為A1配對型、致病性強（新菌系對馬鈴薯與番茄均具強毒性；舊菌系分為馬鈴薯菌系與番茄菌系，致病力相對新菌系較弱，馬鈴薯菌系雖可危害番茄，但番茄菌系不危害馬鈴薯）、耐高溫（新菌系之最高生長溫度為28-29℃；舊菌系為24-25℃）、生長快速、及抗化學農藥滅達樂。其中滅達樂對新菌系菌絲生長抑制濃度（EC50）平均約為200-400 mg/L、舊菌系為0.001-0.005 mg/L，抗藥性提高4-40萬倍。自1997年底至2015年本研究分離的晚疫病菌共有1,766株，均為A1配對型、強抗滅達樂，且目前已分析RG57基因型者均屬於US-11，顯示目前台灣尚未出現A2配對型及其他基因型之晚疫病菌株。"

"Late blight of potato and tomato caused by Phytophthora infestans (Mont.) de Bary is one of the most devastating diseases worldwide. In Taiwan, it was first reported by Kawakami and Suzuki in 1908 and later by Sawada in 1919. Nevertheless, late blight had not been a major threat to the cultivation of potato and tomato ever since as it only occurred sporadically in the highland areas of Taiwan during the wet summer season as well as in the plain areas of northeastern Taiwan during the wet winter and spring seasons. The situation changed abruptly in the 1997 winter, when a severe late blight outbreak occurred in the potato cultivation areas of Holi in the central Taiwan. It then spread to the tomato growth areas of Holi and later all over the entire island of Taiwan within 2 months, causing enormous economic loss in a short period of time. Characterization of the P. infestans isolates collected from the diseased fields indicated that all of them belong to the US-11 lineage (mitochondrial restriction fragment length polymorphism: IIb; allozyme patterns of Pep: 100/100 and Gpi: 100/100/111), different from those collected prior to the 1997 late blight outbreak, which belong to the US-1 lineage (mitochondrial restriction fragment length polymorphism: Ib; allozyme patterns of Pep: 92/100 and Gpi: 86/100). These two lineages of pathogens showed significant differences in several aspects. Especially, when compared to the old US-1 lineage, pathogens of the US-11 lineage displayed faster growth rate (0.45 cm/day vs. 0.19 cm/day at 20℃), better heat tolerance (28-29℃ vs. 24-25℃), and higher metalaxyl resistance (with EC50 of 200400 mg/L vs. 0.001-0.005 mg/L). Continuous surveys of late blight incidence and monitoring of the pathogen indicate that all the P. infestans isolates collected from 1997 to 2015, encompassing 450 isolates from potato and 1,316 isolates from tomato, belong solely to the A1 mating type. Moreover, US-11 appears to be the only P. infestans lineage present in the fields of Taiwan."