Invasions by the Late Blight Pathogen: Renewed Sex and Enhanced Fitness

Abstract

Introductions of Phytophthora infestans, the oomycete plant pathogen responsible for late blight of potato and tomato, have had devastating human impacts wherever they have occurred. This pathogen was apparently sequestered in central Mexico until the mid-19th century, when introductions into the USA and Europe led to a series of crop failures – the most notable of which resulted in the Irish potato famine. A second series was documented in the late 20th century. There were terrible effects also from the second set of introductions, but no population was as vulnerable as the Irish peasants in the mid-19th century. Examination and comparison of these introductions has taught us that we must be prepared for the invasion of species that are more fit than the current population.