Potato famine pathogen “more virulent”

Potatoes_stacked_dirty_blogThe pathogen that caused a famine that killed a million people in the 1800s is more virulent today than it was two centuries ago, researchers have found.

Researchers from North Carolina State University and the University of Copenhagen compared genes from five 19th century strains of Phytophthora infestans, the pathogen behind the potato blight, to modern strains of the pathogen. They found some striking differences between the modern and centuries-old strains – mainly that some genes in the modern strain made P. infestans more virulent to plants than older strains. In one case, an allele named AVR3a, was found to be virulent in modern samples whereas it was non-virulent in historical samples, according to a statement from North Carolina State University.

The study also found P. infestans was brought to Europe more than once, rather than arriving only once and expanding.

“The genetic blueprints, or genotypes, of the historical strains were distinct from modern strains, and genes related to infection were also quite different,” said North Carolina Plant Pathologist Jean Ristaino in a statement. “In the areas of the genome that today control virulence, we found little similarity with historical strains, suggesting that the pathogen has evolved in response to human actions like breeding more disease-resistant potatoes.”

From 1846 to 1851, about one million people died in Ireland from starvation and disease following the potato blight. About two million left the country in the decade following 1845. In modern times, more than $6 billion is spent annually on P.infestans mitigation and damage.

“Late blight is still a major threat to global food security in the developing world,” Ristaino said. “Knowing how the pathogen genome has changed over time will help modern-day farmers better manage the disease.”

Earlier this year, researchers in the United Kingdom identified an early strain of P. infestans by analyzing dried leaf samples from as far back as 1845 that they believe was responsible for the Potato Famine.

Read the study at Nature Communications.

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