Phytophthora

Abstract

Ever since the potato late blight epidemics of the mid-nineteenth century, members of the oomycete genus Phytophthora have emerged as major pathogens of innumerable crops. Nowadays, with more than fifty species recognized and with destructive diseases caused on thousands of plant species, Phytophthora remains an active subject of research and a nagging problem to farmers and growers. Renewed interest in Phytophthora diseases occurred in recent years with the reemergence of Phytophthora infestans, the Irish potato famine fungus. Late blight has turned into a global threat to potato and tomato production following a series of severe late blight epidemics that coincided with the migration to Europe and North America of aggressive A2 mating type strains (Fry and Goodwin, 1997a; Fry and Goodwin, 1997b). The International Potato Center estimated that worldwide losses in potato production caused by late blight have recently exceeded $3 billion annually, making P. infestans the single most important biotic constraint to global food production (Anonymous, 1996).