Phytophthora infestans, the fungus responsible for the Irish potato famine of 1846 that killed an estimated one million people, probably originated in South America. That’s the conclusion researchers from North Carolina State University reached after analyzing the DNA of 183 samples of the fungus from all over the world dating back to 1846.
The particular lineage of the fungus called FAM-1 that caused the Irish famine also caused outbreaks of potato late blight two years earlier in the United States. Its presence in older samples from Colombia suggested a South American origin. Jean Ristaino, one of the researchers, theorized that the pathogen arrived in Europe via infected potatoes on South American ships or directly from infected potatoes from the United States.
Read more in Study Provides Evidence on Movement of Potato Famine Pathogen by Mick Kulikowski on the North Carolina State University website (2016)
The full-text of the scientific paper is available: Historic Late Blight Outbreaks Caused by a Widespread Dominant Lineage of Phytophthora infestans (Mont.) de Bary (2016)