The deadly plant pathogen that caused the Irish potato famine of the 1840s — Phytophthora infestans — is actually more virulent now than ever before, as the result of the arms race between the pathogen and modern agriculture, new research has found. Over $6.2 billion dollars are spent every year in an attempt to stay one step ahead of the pathogen, and to limit the damage that it causes.
As the new research reports — the deadly Irish potato blight pathogen of the 1840s lives on today, with a somewhat different genetic blueprint and an even larger array of weapons. The new work — done by North Carolina State University plant pathologist Jean Ristaino and colleagues Mike Martin and Tom Gilbert from the University of Copenhagen — was done by comparing the genomes of five different 19th century strains of the Phytophthora infestans pathogen with the strains of the pathogen that are present today in the world, which still cause extensive damage every year to potatoes and tomatoes in spite of modern control methods.
What the researchers found was that “the genes in historical plant samples collected in Belgium in 1845 as well as other samples collected from varied European locales in the late 1870s and 1880s were quite different from modern-day P. infestans genes, including some genes in modern plants that make the pathogen more virulent than the historical strains. In one example, a certain gene variant, or allele, called AVR3a that was not virulent in the historical samples was shown to be virulent in the modern-day samples.”
“The genetic blueprints, or genotypes, of the historical strains were distinct from modern strains, and genes related to infection were also quite different,” Ristaino states. “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.”
The researchers note that “some of the differences between the European historical samples from the 1840s and the 1870s and 1880s suggest that the pathogen was brought to Europe more than once, debunking the theory that the pathogen was introduced once and then expanded its range. Ristaino believes it was introduced to Europe multiple times, probably from South American ships.”
“P. infestans caused massive and debilitating late-blight disease outbreaks in Europe, leaving starvation and migration in its wake after ravaging Ireland in the mid-to-late 1840s. Ristaino’s previous work pointed the finger at the 1a strain of P. infestans as the Irish potato-famine pathogen and traced its probable origin to South America.”
“Late blight is still a major threat to global food security in the developing world,” she continues. “Knowing how the pathogen genome has changed over time will help modern-day farmers better manage the disease.”
The new research was just published in the journal Nature Communications.