After 168 years, scientists have finally figured out why the Irish potato famine occurred when a disastrous pest hit Ireland in 1845, resulting in one million deaths.
A team of researchers analyzed plant samples collected in the mid 19th century and believe they have discovered the pathogen that eventually led to the potato blight. DNA from these museum specimens confirms that it is related to similar strains that continue to plague modern day potato and tomato crops today. Luckily, the exact strain of the pathogen is most likely now extinct.
The research team, based out of The Sainsbury Laboratory in Norwich, made the discovery by tracing the pathogen from the early 1800s all the way to the present. They studied dried leaves kept in museum collections at the Kew Royal Botanical Gardens in the United Kingdom and Botanische Staatssammlung Munchen in Germany.
Recent advances in DNA sequencing techniques allowed them to then decode the pathogen's DNA. These were then compared to modern day variants from American, African and European regions.
"This strain was different from all the modern strains that we analysed - most likely it is new to science," researcher Sophien Kamoun told BBC News.
"We can't be sure but most likely it's gone extinct."
Researchers now believe that the pathogen, called HERB-1, originally came about in the early 1800s and continued to spread through the 19th century. In the 20th century, as more potato varieties were introduced, it was eventually replaced by another strain of Phytophthora infestans called US-1.
"Perhaps this strain became extinct when the first resistant potato varieties were bred at the beginning of the 20th Century," said researcher Kentaro Yoshida.
"What is certain is that these findings will greatly help us to understand the dynamics of emerging pathogens. This type of work paves the way for the discovery of many more treasures of knowledge hidden in herbaria."
The research was published in the journal eLife.