Warwick, United Kingdom
July 21, 2009
Researchers at the
University of Warwick
have recovered significant DNA information from a lost form of
ancient barley that triumphed for over 3000 years seeing off: 5
changes in civilisation, water shortages and a much more popular
form of barley that produces more grains. This discovery offers
a real insight into the couture of ancient farming and could
assist the development of new varieties of crops to face today's
climate change challenges.
The researchers, led by Dr Robin Allaby from the University of
Warwick's plant research arm Warwick HRI, examined
Archaeobotanical remains of ancient barley at Qasr Ibrim in
Egypt's Upper Nile. This is a site that was occupied for over
3000 years by 5 successive cultures: Napatan, Roman, Meoitic,
Christian and Islamic.
The first surprise for the researchers was that throughout that
period every culture seemed to be growing a two rowed form of
barley. While natural wild barley tends to be two rowed most
farmers prefer to grow a much higher yield 6 row version which
produces up to 3 times as many grains. That 6 row version has
grown for over 8000 years and that was certainly grown in the
lower Nile over the same period as Qasr Ibrim was occupied. It
was thought that despite the fact that the rest of Egypt used 6
row barley that the farmers of Qasr Ibrim were perhaps
deliberately choosing to import 2 rowed barley but the
researchers could not understand why that would be so.
The plant scientists were pleased to find that the very dry
conditions at Qasr Ibrim meant that they were able to extract a
great deal of DNA information from barley samples from the site
that dated back 2900 years. This was far better than would
normally be expected from barley samples of that age. This led
to the researchers to a second and much bigger surprise. They
found that the DNA evidence showed that the two rowed barley at
the site wasn't the normal wild two eared barley but a mutation
of the more normally cultivated six rowed barley that had
changed into a two ear form that had continued to be cultivated
for around three millennia.
Dr Robin Allaby said:
"The consistency of the two-row phenotype throughout all the
strata spanning three millennia indicates that the reason for
the reappearance of the two row form is more likely to be
genetic, not environmental. Consequently, the two-row condition
has probably resulted from a gain of a function mutation at
another point in the plants DNA that has also reasserted the
two-row condition from a six-row ancestor"
"There may have been a natural selection pressure that strongly
favoured the two-row condition. One such possible cause we are
currently investigating is water stress. Qasr Ibrim is located
in the upper Nile which is very arid relative to the lower Nile
where six-row remains are found, and studies have shown that
two-row can survive water stress better than six-row"
He concluded that:
"This finding has two important implications. Such strong
selection pressure is likely to have affected many genes in
terms of adaptation. Archaeogenetic study of the DNA of such
previously lost ancient crops could confirm the nature of the
selection pressure and be very valuable in the development of
new varieties of crops to help with today's climate change
challenges. Secondly this crop's rediscovery adds to our respect
for the methods and thinking of ancient farmers. These ancient
cultures utilized crops best suited to their environmental
situation for centuries, rather than the much more popular six
rowed barley they used a successful low grain number yield crop
which could cope far better with water stress."
The research paper entitled "Archaeogenetic Evidence of
Ancient Nubian Barley Evolution from Six to Two-Row Indicates
Local Adaptation" has just been published in
PLoS One. The papers
authors are: by Dr Robin Allaby, Sarah A. Palmer and Jonathan D.
Moore from the University of Warwick's plant research arm
Warwick HRI; Alan J. Clapham from Worcestershire Historic
Environment & Archaeology Service at the University of
Worcester; and Pamela Rose fromThe McDonald Institute for
Archaeological Research, University of Cambridge. |
|
