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The researchers used DNA sequencing techniques on dried potato plant leaves from the 1840s to identify the pathogen.
A research team led by scientists at the Sainsbury Laboratory in Norwich, UK, has identified the strain of fungus that caused the potato blight which triggered the 1840s Irish famine.
One million people — one-eighth of the population of Ireland — died of starvation or disease between 1846 and 1851.
The researchers used high-tech DNA sequencing techniques on dried potato plant leaves from the late 1840s stored in collections at the Kew Royal Botanical Gardens in the UK and Botanische Staatssammlung Munchen in Germany.
They call the newly discovered strain HERB-1.
"This strain was different from all the modern strains [of Phytophthora infestans] that we analyzed," Sophien Kamoun of the Sainsbury Laboratory told BBC News. "We can't be sure but most likely it's gone extinct."
The researchers note that a later strain of P. infestans, US-1, became the dominant potato pathogen after new pest-resistant potato varieties were created in the 20th century, according to Smithsonian Magazine.
US-1 is currently responsible for destroying potato crops around the world, while other strains of the pathogen do damage in Mexico.
“These findings will greatly help us to understand the dynamics of emerging pathogens,” Kentaro Yoshida of the Sainsbury Laboratory told BBC News. “This type of work paves the way for the discovery of many more treasures of knowledge hidden in herbaria."
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