Davis, California
December 4, 2006
In a research discovery that has
practical implications for improving wheat varieties, a team of
scientists at the University of
California, Davis, and the
U.S. Department of Agriculture have cloned a gene that
controls the flowering time of barley and wheat.
Differences in this gene, called VRN3, are essential for
adapting these two important crop species to different climates.
The findings of the study, conducted by Professor Jorge
Dubcovsky, a wheat breeder and leader of the UC Davis research
group, and by plant geneticist Ann E. Blechl of the USDA's
Agricultural Research Service in Albany, Calif., will appear the
week of Dec. 4 in the online issue of the Proceedings of the
National Academy of Sciences of the U.S.A.
One of the critical differences that help wheat and barley adapt
to different environments is the existence of winter and spring
forms.
Winter wheat and barley varieties are planted in the fall but
wait until the very cold winter weather passes before flowering.
This requirement for a long-term exposure to low temperatures to
flower is called the "vernalization requirement."
In contrast, spring wheat and barley varieties do not have this
vernalization requirement and can be planted in the spring. This
is essential for regions of the world where winter weather is so
severe that cereals cannot be planted in the fall.
The vernalization requirement in barley and wheat is very
flexible, Dubcovsky noted.
"During the domestication of these species, the different
mutations that occurred in the vernalization genes were selected
by humans, resulting in spring varieties better adapted to
certain regions," he said. "This flexibility has helped wheat to
become one of the world's most important crops."
The Food and Agriculture Organization of the United Nations
estimates that wheat now provides 23 percent of the food
available for daily human consumption around the world.
The vernalization requirement in wheat and barley is controlled
by three major vernalization genes designated VRN1, VRN2 and
VRN3. The first two genes were cloned two years ago by the same
group of researchers.
The cloning of VRN3 now completes a 10-year research project to
understand the genetic regulation of the vernalization
requirement in barley and wheat. Results from this new study
show that mutations in regulatory regions of the VRN3 gene are
responsible for the evolution of several barley and wheat spring
lines.
To confirm that they had identified the correct gene, the
researchers transformed, or genetically altered, the winter
wheat variety Jagger with the VRN3 gene from the spring variety
Hope. The genetically modified plants showed the early flowering
characteristic of the spring wheat varieties, whereas the
control non-transgenic plants failed to flower in the absence of
vernalization. This result confirmed that the gene cloned by
this research team was the correct one.
"The VRN3 mutation we discovered in the wheat variety Hope can
now be used to accelerate flowering time of other wheat
varieties,"
Dubcovsky said. "The VRN3 molecular markers developed in this
study will help breeders to detect the mutations present in
their breeding lines and to study their effects on the
adaptability of wheat and barley varieties to particular
environments."
Funding for this research was provided by the National Research
Initiative of the USDA Cooperative State Research, Education and
Extension Service.
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