RNA Sequencing of 750-Year-Old Barley Virus Sheds New Light on the Crusades 6 February 2014

RNA sequencing of 750-year-old barley virus sheds new light on the Crusades 6 February 2014

Scientists have for the first time sequenced an Dr Robin Allaby of the School of Life Sciences at ancient RNA genome – of a barley virus once the University of Warwick, who led the study, said: believed to be only 150 years old - pushing its "It is important to know as much as we can about origin back at least 2,000 years and revealing how virus evolution as emerging infectious plant intense farming at the time of the Crusades diseases are a growing threat to global food contributed to its spread. security, and of those viruses account for almost half. Researchers at the University of Warwick have detected and sequenced the RNA genome of "History tells us about the devastation caused by Barley Stripe Mosaic Virus (BSMV) in a 750-year- the emergence of disease from wild hosts in old barley grain found at a site near the River Nile disparate countries, such as the Central American in modern-day Egypt. Their study is published in origin of the oomycete that led to the Irish potato the journal Scientific Reports. famine.

This new find challenges current beliefs about the "We need to build up an accurate picture of the age of the BSMV virus, which was first discovered evolution of different types of virus so we can make in 1950 with the earliest record of symptoms just better decisions about policies on plant movement. 100 years ago. "The medieval RNA from Qasr Ibrim gives us a vital Although ancient DNA genomes have been clue to unlock the real age of the Barley Stripe sequenced before, ancient RNA genomes have Mosaic Virus. not been as RNA breaks down more rapidly than DNA – generally around 50 times as fast. "It is very difficult to understand how a plant disease evolved by solely relying on recent However in extremely dry conditions, such as samples, however this 750-year-old example of the those at the site in Qasr Ibrim in Lower Nubia virus allows us to more accurately estimate its where the barley was found, RNA can be better evolution rates and date of origin. preserved and this has allowed the scientists to successfully sequence its genome. "Without the Medieval RNA evidence, the virus appears to be much younger than it actually is, Using the new medieval RNA to calibrate when in fact its origins go back thousands of years. estimates of the rate of mutations, the researchers were able to trace the evolution of the Barley "It's possible that other viruses that similarly appear Stripe Mosaic Virus to a probable origin of around to be very recent may in fact have a more ancient 2,000 years ago, but potentially much further back origin." to the domestication of barley in the Near East around 11,000 years ago. The researchers believe that the Medieval BSMV genome came from a time of rapid expansion of the BSMV is transmitted through seed-to-seed contact plant disease in the Near East and Europe. so it is likely to originally have been transferred from the wild grass population to an early This coincided with the tumult of the Crusades cultivated form of barley while the seeds were which saw the Christian lands of Europe take arms stored. against the Muslim territories of the Near East with their sights set on the city of Jerusalem. The

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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.

In more recent history, the virus appears to have spread to the US from Europe around 120-150 years ago.

Provided by University of Warwick APA citation: RNA sequencing of 750-year-old barley virus sheds new light on the Crusades (2014, February 6) retrieved 2 October 2021 from https://phys.org/news/2014-02-rna-sequencing-year-old- barley-virus.html

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