"We need to build up an accurate picture of the evolution of different types of virus so we can make better decisions about policies on plant movement.
"The medieval RNA from Qasr Ibrim gives us a vital clue to unlock the real age of the Barley Stripe Mosaic Virus.
"It is very difficult to understand how a plant disease evolved by solely relying on recent samples, however this 750-year-old example of the virus allows us to more accurately estimate its evolution rates and date of origin.
"Without the Medieval RNA evidence, the virus appears to be much younger than it actually is, when in fact its origins go back thousands of years.
"It's possible that other viruses that similarly appear to be very recent may in fact have a more ancient origin."
The researchers believe that the Medieval BSMV genome came from a time of rapid expansion of the plant disease in the Near East and Europe.
This coincided with the tumult of the Crusades which saw the Christian lands of Europe take arms against the Muslim territories of the Near East with their sights set on the city of Jerusalem. The seventh Crusade of Louis IX in 1234 is the most closely aligned in date to the origin of the virus expansion.
The researchers believe the massive war effort could have caused the virus to spread, fuelled by an intensification of farming in order to feed the armies engaged in the campaign.
This made contact with cultivated barley and wild grass more likely, providing opportunities for the virus to 'jump' into the crop.
Genetic evidence also points to a split into an east and west BSMV lineage around the end of the 15th century, around 100 years after the Mongol Empire stabilised the Silk Road. It is likely that BSMV was transported to the east via trade routes such as the Silk Road in the late Medieval period.
|Contact: Luke Harrison|
University of Warwick