What Happened To The Disease That Caused The Irish Potato Famine?

Jul 19, 2013

Potato late blight lesion
Credit Jean Ristaino, NC State University

New research reveals the disease that wiped out millions of potatoes and led to widespread famine in Ireland is still around, and it’s more virulent than ever.  A new study led by NC State University plant pathologist Jean Ristaino investigates the history of the fungus-like organism that caused the Irish potato famine and how its genome has evolved since it first showed up in Ireland in the 1800’s.

Phytophthora infestan, or “late blight,” as it’s known to gardeners and farmers, is a widespread disease found all over the world, including farms and backyard gardens in North Carolina.  It was one of the first plant pathogens ever described by scientists.  Dr. Ristaino first became interested in studying the pathogen when she took a sabbatical overseas ten years ago and saw firsthand ancient samples of diseased leaves from the potato famine.

“I started doing DNA work on those leaves many years ago, but in those days we were only able to amplify a few genes,” she said. “Now, prices have come down, technology has advanced, and we’re able to sequence the entire genome.”

A visualization of the late blight genome.
Credit Jean Ristaino, NC State University

That’s exactly what she and her research team, which included scientists from the University of Copenhagen, Duke, and UNC-Chapel Hill, did. They mapped the entire genomes of various samples of the late blight pathogen, starting with ones from 1845, and moving up through the years to modern day samples. No one had ever studied the temporal changes in the pathogen so closely, and the results were surprising.

“We found at least two distinct lineages that have diverged between 1845 and 1875, which indicates there was probably more than one introduction of pathogen into Europe,” Ristaino said. “That would make sense, because we think they originated from the Andean region of South America.”

The researchers also found that strains of modern day late blight are more aggressive than ever been before, something they determined by analyzing plant proteins.

Ristaino says that there's a possibility that people could use their findings to help control the disease and develop plants resistant to the pathogen.