Experts map genome of pathogen responsible for potato famine

Researchers studying the spread of late blight say a recent discovery is important, even if they’re more than 150 years late.

In a paper published last month, an international team of researchers identified a new strain of Phytophthora infestans, the pathogen that causes the disease in potato crops around the world, which they believe to be the culprit behind the Irish Potato Famine of the 19th century.

It’s the first time dried herbarium or plant samples have been used to map the genome of a pathogen.

By examining the source of the epidemic, which resulted in a million deaths, researchers today can better understand how plant pathogens develop, said Hernan Burbano of Germany’s Max Planck Institute for Developmental Biology.

“Potato is the third largest food crop and late blight is its most destructive disease, which makes late blight a big threat to food security,” wrote Burbano in an e-mail to The Western Producer.

“This disease results in annual losses that would be sufficient to feed from 80 to many hundreds of millions of people.”

A separate team first mapped the genome of P. infestans in 2009, but until now it was believed that a single strain, US-1, was behind most late blight outbreaks all the way through to the late 1970s. By studying historic and modern samples from across the globe, researchers identified a new strain, HERB-1.

The new strain, a close relative of US-1, is believed to have emerged in the early 1800s at the time of first contact between Americans and Europeans in Mexico. It persisted in Europe for at least 50 years.

“The understanding of pathogen dynamics through time should help us better predict future changes in pathogen distributions,” wrote Burbano.

Researchers note that the newly discovered strain is absent from modern samples, which may indicate it went extinct at the turn of the 20th century — when US-1 became dominant — alongside the introduction of plant breeding and new varieties.

“It has also shown us how the spread of pathogens is strongly associated with human activity,” wrote Burbano.

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