SCIENTISTS AT A research institute in Germany have figured out what caused the potato blight during the Great Famine, using dried potato plants that are over 120 years old.

Researchers at the Max Planck institute announced they have identified the exact strain that caused “all this havoc” in Ireland.

For the first time researchers have decoded the genome of a plant pathogen and its plant host from dried samples. This opens up a whole new area of research into how pathogens evolve and how human activity impacts the spread of plant disease.

A team of moleclar biologists from Europe and the US reconstructed the spread of the potato blight pathogen ‘Phytophthora infestans’ from these dried plants:

(Image: Marco Thines/Senckenberg Gesellschaft für Naturforschung)

The 11 historical samples from potato leaves came from Ireland, the UK, Europea and North America. Even though they were between 120 and 170 years old, they were still found to have many intact pieces of DNA.

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

“Herbaria represent a rich and untapped source from which we can learn a tremendous amount about the historical distribution of plants and their pests – and also about the history of the people who grew these plants,” Kentaro Yoshida from The Sainsbury Laboratory in Norwich added.

The researchers examined the historical spread of the fungus-like pathogen that caused the Irish potato famine and concluded that a strain new to science was responsible for the fatal outbreak. It was previously thought that a strain called US-1 was the culprit.

Samples were compared with modern strains from around the world and scientists were able to estimate when the various strains diverged from each other over time.

The authors of the research said this now paves the way for further “treasures” hidden in herbaria to be uncovered.

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