Late blight, the disease responsible for the Irish potato famine in the 1840s, has evolved over the years to become an even nastier foe.
North Carolina State University plant pathologist Jean Ristaino, along with colleagues Mike Martin and Tom Gilbert from the University of Copenhagen, compared the genetic make-up of pathogen samples taken back then to the current disease, according to a news release.
The researchers found the genes in samples collected in Belgium in 1845 as well as other samples collected in Europe during the 1870s and 1880s were vastly different from the genes of today's Phytophthora infestans.
For example, one gene variant was not virulent in the historic samples but it is in modern-day samples.
Some of the genetic differences suggest the pathogen was brought to Europe more than once.
This contradicts the theory that the pathogen was introduced just once and then expanded its range.
Earlier work pointed the finger at the 1a strain of P. infestans as the cause of the Irish potato famine. It most likely originated in South America.
By studying how the pathogen's genetic make-up has changed over time, researchers can develop program to better manage the disease, according to the release.