Study Presents Evidence on Movement of Potato Famine Pathogen

Researchers at North Carolina State University (NC State) have presented evidence on the movement and evolution of Phytophthora infestans, the pathogen that caused the Irish potato famine in the 1840s, which set down roots in the United States before attacking Europe.

NC State plant pathologists studied 12 key regions on the genomes of 183 historic and modern pathogen samples from across the globe to track the evolution of differing strains of P. infestans. The study shows that a lineage called FAM-1 caused outbreaks of potato late blight in the United States in 1843, and in Great Britain and Ireland two years later. It was also found in historic samples from Colombia, suggesting a South American origin. FAM-1 caused massive and debilitating late blight disease outbreaks in Europe. Jean Ristaino, the corresponding author of the study, theorizes that the pathogen arrived in Europe via infected potatoes on South American ships, or directly from infected potatoes from the United States.

FAM-1 survived for about 100 years in the United States, until it was displaced by a sister lineage called US-1 which in turn was elbowed out by more aggressive strains of the pathogen that came from Mexico.

For more details of the study, read the news release from NC State.