DNA used to finger culprit in historic Irish potato famine

Researchers in Germany say they've identified a unique strain of potato blight responsible for the disastrous potato famine in 19th-century Ireland. Researchers at the Max Planck Institute for Developmental Biology reported they used dried herbarium samples to decode the genome of the variety of the plant pathogen Phytophthora infestans that changed the course of Irish history. "We have finally discovered the identity of the exact strain that caused all this havoc," Hernan Burbano said in an institute release Tuesday. While a strain of the fungus-like pathogen known as US-1 has long been thought to have caused the fatal outbreak, the new study suggests a strain new to science was responsible, the researchers said. While more closely related to the US-1 strain than to other modern strains, it is unique, Burbano said. "Both strains seem to have separated from each other only years before the first major outbreak in Europe," he said. In the study the researchers decoded the entire genomes of 11 historical samples of Phytophthora infestans from potato leaves collected over more than 50 years. Gathered from Ireland, Britain, Europe and North America, the leaf samples had been preserved at the Botanical State Collection Munich and the Kew Gardens in London.