Potato-Blight Strain in Irish Famine Is Identified by Scientists

The Irish potato famine of the 1840s was caused by a plant-pathogen strain that was unknown until now, scientists said after examining dried leaves that were as much as 170 years old.

A strain of Phytophthora infestans called HERB-1 that probably emerged early in the 19th century caused the disaster, the Tuebingen, Germany-based Max Planck Institute for Developmental Biology said today in a statement on its website. Until now, the US-1 strain was “long thought” to have been responsible, it showed.

Ireland lost almost a quarter of its population to death or emigration between 1845 and 1850, according to the website of the Irish National Famine Museum in Strokestown, County Roscommon. U.S. and European molecular biologists studied dried plants to reconstruct the pathogen’s spread for research to be published in the eLife journal, the statement showed.

“We have finally discovered the identity of the exact strain that caused all this havoc,” the institute’s Hernan Burbano said in the statement. HERB-1 is unique even though it is related to US-1, according to the organization.

The scientists decoded the complete genomes of 11 samples of Phytophthora infestans from potato leaves collected over more than 50 years from Ireland, the U.K., Europe and North America, the institute said. The samples were preserved by the Botanical State Collection Munich and Kew Gardens in London, it said.

“The degree of DNA preservation in the herbarium samples really surprised us,” Johannes Krause of the University of Tuebingen, a co-author of the study, said in the statement.

In addition to Burbano and Krause, authors of the study included Kentaro Yoshida of the Sainsbury Laboratory in Norwich, England, and Frank Martin of the U.S. Department of Agriculture, the statement showed. Funding came from organizations including the European Research Council and the Gatsby Charitable Foundation.

To contact the reporter on this story: Dan Weeks in London at dweeks1@bloomberg.net

To contact the editor responsible for this story: Alaric Nightingale at anightingal1@bloomberg.net

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