Irish potato famine pathogen outbreaks have stoked on six continents
Researchers at North Carolina State University continue to track the evolution of different strains of the plant pathogen that caused the Irish potato famine in the 1840s, which took hold in the United States. United before attacking Europe.
North Carolina state plant pathologists studied the genomes of approximately 140 pathogen samples – both historic and modern – from 37 countries on six continents to track the evolution of different strains of Phytophthora infestans, a major cause of late blight on potato and tomato plants.
The study, published in Scientific reports, shows that the historic line called FAM-1 was found in almost three-quarters of the samples (73%) and was found on all six continents.
“FAM-1 was much more widespread than previously assumed, stretching from Europe to Asia and Africa along the trade routes of the British colonies,” said Jean Ristaino, professor emeritus of plant pathology William Neal Reynolds and corresponding study author. “The lineage has also been found over a period of over 140 years.”
FAM-1 caused outbreaks of potato late blight in the United States in 1843, and then two years later in Britain and Ireland. It has also been found in historical samples from Colombia – suggesting a South American origin. FAM-1 has caused massive and debilitating outbreaks of late blight in Europe, leaving in its wake famine and migration. Ristaino hypothesizes 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, but was later displaced by a different strain of the pathogen called US-1, Ristaino said.
“US-1 is not a direct descendant of FAM-1, but rather a sister line,” said Ristaino. “We found US-1 in 27% of the study samples and they were found much later.”
US-1 has since been expelled from the United States by even more aggressive strains of the pathogen originating in Mexico. Winter tomato crops – grown in Mexico and imported into the United States – harbor the pathogen, Ristaino said.
The study also suggests that the pathogen first spread to potatoes and then spread to tomatoes. Spread of the pathogen in ripe tomatoes in ships’ holds would have been unlikely, Ristaino said.
The pathogen’s effects are not limited to the decimation of the Irish potato harvest 175 years ago. Billions are spent around the world every year trying to control the pathogen, Ristaino said. Potatoes in developing countries are particularly vulnerable because fungicides are less available and often unaffordable.
Amanda Saville, research technician, works in the Ristaino laboratory and is co-author of the article. Funding was provided by the Agriculture and Food Research Initiative of the United States Department of Agriculture (Grant 5197-NCSU-USDA-3179 and Grant 2011-68004-30154) and by the North Carolina Agricultural Research Service.
“Historical global pandemics caused by the FAM-1 genotype of Phytophthora infestans on six continents ”
Authors: Amanda C. Saville and Jean B. Ristaino, North Carolina State University
Posted: June 11, 2021 to Scientific reports
DO I: 10.1038 / s41598-021-90937-6
Abstract: The FAM-1 genotype of Phytophthora infestans caused late blight in the 1840s in the United States and Europe and was responsible for the Irish famine. We examined 140 herbarium specimens collected between 1845 and 1991 from six continents and used 12-plex microsatellite (SSR) genotyping to identify FAM-1 and the mtDNA lineage (Herb-1 / Ia) present in historical samples. . FAM-1 has been detected in approximately 73% of historical specimens and has been found on six continents. The US-1 genotype was found later than FAM-1 on all continents except Australia / Oceania and in only 27% of samples. FAM-1 was the first genotype detected in almost all of the former British colonies from which samples were available. Data from historical epidemic samples suggests that the FAM-1 genotype was widespread, diverse, and widespread in Asia and Africa from European sources. The famine lineage spanned six continents for 144 years, remained widespread, and probably spread during global colonization from Europe. In contrast, modern lines of P. infestans are rapidly displaced and sexual recombination occurs in some areas.