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Tracking A Fungus
	Samples from Irish Potato Blight May Shed Light on Crop-Killer Farmers tend to rows of potatoes in Maryland. Using 150-year-old potato leaves, U.S. researchers hope to determine how the Irish potato famine began in the 1840s. (Ric Dugan/AP Photo)

The Associated Press
R A L E I G H, N.C., March 21 A researcher is using DNA analysis of 150-year-old potato leaves to get to the bottom of Ireland’s Great Potato Famine of the 1840s, which sent a huge wave of immigrants across the Atlantic to America.
Jean Ristaino, a plant pathologist at North Carolina State University since 1987, has identified DNA from the pathogen, Phytophthora infestans, in the dried leaves of blight-stricken potatoes preserved from the famine.
“We are the first group to successfully (replicate) plant pathogen DNA from old historic samples,” said Ristaino. “Now what I want to do is track where it came from.”

One Million Starved
Her breakthrough could lead others to perform genetic analysis on preserved samples of plant life to track down other crop killers.
     The famine killed more than a million Irish during the mid-19th century and dispersed a million more to other countries.
     A blight destroyed the British colony’s chief staple. English leaders continued to export crops and livestock out of the colony instead of feeding the people. English landlords evicted tens of thousands of Irish from their homes during the famine for nonpayment of rent.
     Fungicides have helped control the blight, but scientists still don’t know for certain where the fungus-like pathogen originated and how it got to Ireland.
     Two years ago, Ristaino toured herbariums in England, Boston and Maryland and got permission to take 150-year-old samples of dried potato leaves.
     Using a genetic screen she developed, she extracted DNA fragments of the late blight pathogen and replicated them. That allowed her to sequence a minute section of DNA.
     Comparing the sequenced sections to a present-day sample of late blight confirmed the disease had killed them.

Spanish Introduced Staple to Europe
Her genetic screening tool, a chemical primer that binds with that sequenced section of DNA, has been patented by NCSU. Ristaino hopes it will become a diagnostic tool to identify the blight in seed potatoes before they are planted.
     The next step is to identify the genes specific to the pathogen, which could help scientists trace the fungus’ origin and migration.
     The potato originated in a part of South America that includes modern-day Chile and Peru. Spanish explorers brought the potato back to Europe and to North America, and it became a sustenance crop for the Irish.
     When the blight destroyed the staple, Ireland’s already tenuous farm economy was thrown into crisis. English leaders, however, were strong free-market advocates and did not see the need for government intervention.
     By the time the blight ended in 1850, Ireland had lost a quarter of its 8 million people. Tourists can view the huge mounds topped with a single cross where those who died of starvation were buried in mass graves.

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