Published Tuesday, 21 May 2013
A new study has shed light on the potato famine. (© Getty)
The fungal disease, called HERB-1, came to Ireland via Mexico in the mid-19th century.
Over one million people died in the famine which lasted just under 10 years.
A team of molecular biologists from Europe and America were able to use dried plant material - some of it up to 170 years old - to reconstruct the spread of the deadly blight.
It had been thought that a strain called US-1 was the cause, but it now appears a different but closely-related strain led to the famine.
Hernan Burbano from the Max Planck Institute for Developmental Biology said: "Both strains seem to have separated from each other only years before the first major outbreak in Europe."
Potato blight is caused by the microorganism, Phytophthora infestans, which destroys the leaves of potato crops.
The new study compared historic samples with modern strains.
Scientists said: "The HERB-1 strain of Phytophthora infestans likely emerged in the early 1800s and continued its global conquest throughout the 19th century.
"Only in the twentieth century, after new potato varieties were introduced, was HERB-1 replaced by another Phytophthora infestans strain, US-1."
Eleven historical samples of Phytophthora infestans, from potato leaves collected over more than 50 years across Ireland, the UK, Europe and North America, were used in the research.
The material had been preserved in the herbaria of the Botanical State Collection Munich and Kew Gardens in London.
© UTV News