Features Agronomy Diseases
Research shows late blight pathogen originates from Mexico

June 10, 2014, Florida – A University of Florida scientist has pinpointed Mexico as the origin of the pathogen that caused the 1840s Irish Potato Famine, a finding that may help researchers solve the $6 billion-a-year disease that continues to evolve and torment potato growers around the world.

For more than a century, scientists thought the pathogen that caused late blight originated in Mexico. But a 2007 study contradicted earlier findings, concluding it came from the South American Andes.

Erica Goss, a plant pathology assistant professor at the University of Florida, wanted to clear up the confusion and after analyzing sequenced genes from four strains of the pathogen, found ancestral relationships among them that point to Mexico as the origin.

“The pathogen is very good at overcoming our management strategies,” says Goss. “To come up with better solutions to late blight, we need to understand the genetic changes that allow it to become more aggressive. By understanding past changes, we can design new strategies that are more likely to be robust to future genetic changes.”

Goss and eight colleagues analyzed the genes of potato late-blight pathogens from around the world. Potato late blight, which flourishes in cool, damp weather, is caused by the pathogen phytophthora infestans.

Scientists sequenced four genes from more than 100 phytophthora infestans samples, plus four closely related species, to tease out the pathogen’s origin. Knowing the origin provides insight into its genetic diversity and the ways it adapts to different environments, Goss said

The pathogen also moved from other related species to the potato late in the evolutionary history of potatoes, she said, perhaps one reason potatoes are so susceptible to the disease and why finding a breeding-based solution to the disease has been so difficult.

The pathogen costs $6 billion a year globally between direct crop damage and spraying, she says.

June 10, 2014  By University of Florida