부산대학교 도서관

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 200- 400 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 A^1 mating type. Moreover, US-11 appears to be the only P. infestans lineage present in the fields of Taiwan.