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Ancient potatoes hold key to Irish Famine mystery

Potato samples stored for more than 170 years have helped solve the mystery of why blight caused so many deaths in Ireland during the 19th Century.

UK researchers have discovered that the potato blight that caused the Great Famine of 1845-48 was the same strain which caused a second outbreak some 30 years later.

If the same information was available today, farmers and smallholders would be advised to harvest the crop, eat or sell it but not store any seed potatoes for planting the following year.

Instead, new blight-free seed potatoes would be sourced, eliminating the problem.

"In the 1840s, they didn't even know it was caused by a fungus," Professor Bruce Fitt from the University of Hertfordshire said.

"The problem, as I understood it, was the crop was grown by smallholders. If they destroyed the crop, they would starve.

"In the 1840s, they really didn't understand that it (blight) was caused by a micro-organism," Professor Fitt added.

"There was a great debate that blight was caused by a change in the weather, but they had the foresight to dry and ground potato tubers and store them in the archives. They didn't dream of the things we could do today with molecular biology.

"We understand the epidemiology now, that the pathogen remains in the potato, and when someone plants these the following year the spores rise onto the leaves. This destroys the leaves, resulting in no growth in the plant.

"We asked, was the strain of blight -- phytophthora infestans, which means plant destroyer -- the same in the 1870s as the one which caused the famine of the 1840s?"

Scientists extracted DNA from potato leaf samples dating back to the 1840s, and analysed them for the presence of the blight pathogen.

The pathogen was matched against samples collected in the 1870s, which were dried, ground and stored in glass bottles by Victorian scientists, and it was discovered they were the same strain.

The research will be used to help tackle potato blight today.

"As we understand more as to what happened in the 19th Century, it gives us an insight into what we can do to tackle the problem today. Potato blight today is more difficult to control than a few years ago," he said.

Belfast Telegraph