Irish potato famine pathogen identified

Posted May 22, 2013 by Tim Sandle
Scientists have used plant samples collected in the mid-19th Century to identify the pathogen that caused the Irish potato famine. The fungus is different to the known types of fungi of today.
Phytophthora infestans on a potato
Phytophthora infestans on a potato
According to UPI the fungus has been described as a Phytophthora infestans strain called HERB-1. It was isolated and identified using DNA extracted from museum specimens (analyzed from dried leaves kept in collections in museums at Kew Royal Botanical Gardens, UK).
Phytophthora infestans is a fungus-like pathogen and the causal agent of potato and tomato late blight, a devastating disease of potato and tomato worldwide.
The analysis showed that the strain that changed history (notably the infamous Irish potato famine) is different from modern day epidemics, and is probably now extinct; whereas other strains continue to attack potato and tomato crops around the world.
The major global food spoilage fungus of today is a different strain called Phytophthora infestans strain US-1, genetically distinct from the nineteenth century fungus. The HERB-1 Phytophthora infestans strain resulted in a global nineteenth century food spoilage disease called potato blight. According to Bloomberg, the fungus emerged in the U.S. around 1844 and was reported in areas around the ports of Philadelphia and New York. The disease spread to Europe the following year. The summer of 1845 was mild but very wet, giving the perfect conditions for the blight to spread.
The main location affected was Ireland where the loss of potatoes led to the deaths of about a million people from starvation and disease between 1846 and 1851.
Scientists speculate that the dominant type of crop spoilage fungus has changed as the result of changes to crop breeding methods, which appear to have an impact on the evolution of pathogens.
Commenting on the identification, Plant scientist Kentaro Yoshida told Wired: "Perhaps this strain became extinct when the first resistant potato varieties were bred at the beginning of the twentieth century. What is for certain is that these findings will greatly help us to understand the dynamics of emerging pathogens. This type of work paves the way for the discovery of many more treasures of knowledge hidden in herbaria."
The research was undertaken by the Sainsbury Laboratory, Norwich, U.K. The findings will be published in a new open-access scientific journal called eLife.