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Irish potato famine mystery finally solved, 168 years later

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Potato farmers

Scientists believe that they have finally solved the question of what caused the Irish potato famine which destroyed potato crops in Ireland causing the deaths of millions of people. A research team from Norwich, England, used dried leaf cuttings, some of which were nearly 170 years old, to reconstruct the spread of the HERB-1 strain of Phytophthora infestans, a fungal disease that came to Ireland via Mexico in 1845. Using DNA sequencing techniques, the researchers decoded the genome of the plant pathogen and compared it to modern strains. This allowed them to identify where it emerged and how it spread.

It was originally theorized that the US-1 strain of fungal disease caused the massive destruction of potatoes in Ireland. Now scientists believe the US-1 strain crowded out the devastating HERB-1 variant and became the dominant form partly helped along by changes in crop breeding methods.