Researchers in North Carolina may have pinpointed the movement and evolution of the pathogen that caused the Irish potato famine in the 1840’s that devastated potato crops throughout Europe, causing widespread hunger and death.
In the study, researchers from North Carolina State University track the evolution of differing strains of Phytophthora infestans, the pathogen responsible for the Great Famine and a major cause of late-blight disease on potato and tomato plants around the globe.
The researchers studied 12 crucial regions on the genomes of 183 pathogen samples—both historic and modern—from around the world. The team was able to show a lineage called FAM-1 as the cause of outbreaks of potato late blight in the United States in 1843 and then two years later in Great Britain and Ireland.
They also found historic samples from Colombia suggesting there may have been a South American origin.
Jean Ristaino, William Neal Reynolds Distinguished Professor of Plant Pathology and the corresponding author of the study, explained the damage FAM-1 caused.
“FAM-1 was widespread and dominant in the United States in the mid-to-late 19th century and the early 20th century,” Ristaino said in a statement. “It also was found in Costa Rica and Columbia in the early 20th century.”
According to Ristaino, the pathogen likely arrived in Europe by infected potatoes on South American ships or directly from infected potatoes from the U.S.
She also said that FAM-1 lasted about 100 years in the U.S. but was then displaced by a different strain of the pathogen that was dubbed US-1.
“US-1 is not a direct descendant of FAM-1, but rather a sister lineage,” Ristaino said.
However, US-1 has also been displaced out of its homeland by even more aggressive strains of the pathogen that has originated in Mexico.
While the pathogen is best known for ravaging Ireland’s potato crop nearly two centuries ago, billions continue to be spent worldwide each year in attempts to control the pathogen, according to Ristaino.
During the famine approximately 1 million people died and about a million more emigrated from Ireland, resulting in a population loss of between 20 and 25 percent.
The study was published in PLOS One.
Paper co-authors are Amanda Saville, a research technician in Ristaino’s lab, and Michael Martin, an associate professor with the Norwegian University of Science and Technology. The research was supported by a grant from USDA’s National Institute of Food and Agriculture.