Scientists have for the first time sequenced an ancient RNA genome of a barley virus once believed to be only 150 years old - pushing its origin back at least 2,000 years and revealing how intense farming at the time of the Crusades contributed to its spread.
Researchers at the University of Warwick have detected and sequenced the RNA genome of Barley Stripe Mosaic Virus (BSMV) in a 750-year-old barley grain found at a site near the River Nile in modern-day Egypt. Their study is published in the journal Scientific Reports.
This new find challenges current beliefs about the age of the BSMV virus, which was first discovered in 1950 with the earliest record of symptoms just 100 years ago.
Although ancient DNA genomes have been sequenced before, ancient RNA genomes have not been as RNA breaks down more rapidly than DNA generally around 50 times as fast.
However in extremely dry conditions, such as those at the site in Qasr Ibrim in Lower Nubia where the barley was found, RNA can be better preserved and this has allowed the scientists to successfully sequence its genome.
Using the new medieval RNA to calibrate estimates of the rate of mutations, the researchers were able to trace the evolution of the Barley Stripe Mosaic Virus to a probable origin of around 2,000 years ago, but potentially much further back to the domestication of barley in the Near East around 11,000 years ago.
BSMV is transmitted through seed-to-seed contact so it is likely to originally have been transferred from the wild grass population to an early cultivated form of barley while the seeds were stored.
Dr Robin Allaby of the School of Life Sciences at the University of Warwick, who led the study, said: "It is important to know as much as we can about virus evolution as emerging infectious plant diseases are a growing threat to global food security, and of those viruses account for almost half.
"History tells us about the devastation caused by the emerg
|Contact: Luke Harrison|
University of Warwick