Potato Grower

September 2021

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34 POTATO GROWER | SEPTEMBER 2021 Diggin' In Diggin' In Study finds late blight pathogen stoked outbreaks on six continents World Traveler LATE BLIGHT | By Amanda Saville & Jean Ristaino North Carolina State University researchers continue to track the evolution of different strains of the plant pathogen Phytophthora infestans, which set down roots in the U.S. before attacking Europe and causing the Irish potato famine in the 1840s. NC State plant pathologists studied the genomes of about 140 pathogen samples—historic and modern—from 37 countries on six continents to track the evolution of differing strains of P. infestans, a major cause of late blight disease on potato and tomato plants. The study, published in Scientific Reports, shows that the historic lineage called FAM-1 was detected in nearly three-fourths of the samples (73 per- cent) and was found on all six conti- nents. "FAM-1 was much more widespread than previously assumed, spreading from Europe to Asia and Africa along British colony trade routes," says Jean Ristaino, an NC State professor of plant pathology and the corresponding au- thor (with research technician Amanda Saville) of the study. "The lineage was also found over a span of more than 140 years." FAM-1 caused outbreaks of potato late blight in the U.S. in 1843 and then two years later in Great Britain and Ireland. It was also found in historic samples from Colombia, suggesting a South American origin. FAM-1 caused massive and debilitating late blight outbreaks in Europe, leaving starvation and migration in its wake. Ristaino theorizes that the pathogen arrived in Europe via infected potatoes on South American ships or directly from infect- ed potatoes from the U.S. FAM-1 survived for about 100 years in the U.S. but was then displaced by a different strain of the pathogen called US-1, Ristaino says. "US-1 is not a direct descendant of 2361-3Broekema12h.indd 1 7/18/19 3:09 PM

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