Irish potato famine microbe traced to Mexico

The Irish potato famine was triggered by the pathogen P. infestans, which probably originated in the Toluca Valley and nearby regions of Mexico.

Courtesy of Niklaus J. Grünwald

The pathogen that triggered the Irish potato famine in the 1840s probably originated in central Mexico, not in the Andes, as some studies had suggested.

A genetic analysis of the pathogen, Phytophthora infestans, and its closest known relatives suggest that the microbes found in the Andes are descendants of the Mexican-based pathogens, scientists report June 2 in the Proceedings of the National Academy of Sciences.

The finding appears to resolve the debate over two competing theories of where the microbe came from and could help with efforts to develop crops that are resistant to P. infestans infestations.

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

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