The Irish Potato Famine Altogether, about a million people in Ireland are estimated to have died of starvation and epidemic disease between 1846 and 1851 
 
 Some two million emigrated in a period of a little more than a decade from 1845 
 
 Comparison with other famines suggests the Irish famine of the late 1840s, which killed nearly one-eighth of the entire population, was proportionally much more destructive of human life than the vast majority of famines in modern times 
 
 The famine began as a natural disaster, but historians say its effects were worsened by the actions and inactions of the Whig government of the time Source: BBC History 
 
 Researchers in the UK, Germany and the US analysed dried leaves kept in collections in museums at Kew Royal Botanical Gardens, UK, and Botanische Staatssammlung Munchen, Germany. It is the first time scientists have decoded the genome of a plant pathogen and its plant host from dried herbarium samples. DNA extracted from museum specimens shows the strain that changed history is different from modern day epidemics, and is probably now extinct. Until now, it has been unclear how early strains of Phytophthora infestans are related to those present in the world today. For research to be published in eLife, a team of molecular biologists from Europe and the US reconstructed the spread of the potato blight pathogen from dried plants. "This strain was different from all the modern strains that we analysed - most likely it is new to science," Prof Sophien Kamoun of The Sainsbury Laboratory told BBC News. The researchers compared the historic samples with modern strains from Europe, Africa and the Americas as well as two closely related Phytophthora species. Treasures of knowledge 
 
 The researchers believe the strain - HERB-1 - emerged in the early 1800s and continued to spread globally throughout the 19th Century. Only in the 20th Century, after new potato varieties were introduced, was it replaced by another Phytophthora infestans strain, US-1, which is now dominant around the world. Image caption Potato blight is a major problem today 
 
 The research, published in the new open-access scientific journal, eLife, suggests crop breeding methods may have an impact on the evolution of pathogens. "Perhaps this strain became extinct when the first resistant potato varieties were bred at the beginning of the 20th Century," said Kentaro Yoshida from The Sainsbury Laboratory. "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."
– Nearly two centuries later, researchers believe they have identified the pathogen that led to Ireland's deadly potato famine. To make their discovery, British, German, and American scientists sequenced DNA from samples of dried potato leaves collected between 120 and 170 years ago, reports PhysOrg. They identified the particular strain of Phytophthora infestans in samples dating to 1845, the year the pathogen arrived in Ireland, then compared the genetic information to that of today's plants, the BBC reports. As PhysOrg explains, researchers had previously believed US-1, today's major pathogen, was the culprit. Instead, they found that a new strain, dubbed HERB-1, triggered the outbreak. Scientists believe HERB-1 appeared at the beginning of the 19th century and wasn't replaced by US-1 until the 20th century, when new potato varieties were planted. ("We can't be sure but most likely [HERB-1 has] gone extinct," says one scientist.) Besides solving a 168-year-old mystery, the find has big implications: It marks the first time the genome of a plant pathogen has been decoded using dried, preserved plant specimens, and paves the way for similar research in the future.