In the game of wheat genetics, Jorge Dubcovsky's laboratory at UC Davis has hit a grand slam, unveiling for the fourth time in a dozen years a gene that governs wheat vernalization, the biological process requiring cold temperatures to trigger flower formation.
Identification of the newly characterized VRN-D4 gene and its three counterpart genes is crucial for understanding the vernalization process and developing improved varieties of wheat, which provides about one-fifth of the calories and proteins that we humans consume globally.
The new study, reported online in the Proceedings of the National Academy of Sciences, also shows how the spring growth habit in some wheat varieties traces back to ancient wheat that grew in what is now Pakistan and India.
Different wheat for different climates:
Wheat first appeared about 8,000 years ago in the coastal area of the Caspian Sea, where Europe and Asia converge. It quickly spread through both continents and now grows worldwide. Scientists attribute its adaptability to its rapidly changing genome and the fact that most types of wheat have two or three sets of chromosomes.
In cold climates, the vernalization process ensures that the cold-sensitive flowering parts of the wheat plant develop only after winter's harshest months have passed and just in time for the warmer weeks of spring. Such "winter wheat" is planted in the fall and harvested in early summer.
In contrast, "spring wheat" varieties don't have a vernalization requirement and can be planted in spring and harvested in fall. This is essential for regions where winters are so severe that wheat cannot be sown in fall and grown through the winter months.
Vernalization key to wheat's adaptability:
"We're extremely interested in understanding the adaptive changes, especially vernalization, which occurred in wheat during the early expansion of agriculture, said study first-author Nestor Kippes, a doctoral candidate in the Dubcovsky lab.
Because vernalization governs flowering time, it's important to a plant's reproductive success and key to maximizing grain production in wheat, barley and other cereal crops, Kippes said.
Although the world produces more than 700 million tons of wheat annually, the rapidly growing global human population continues to press for even greater production of wheat and other staple crops. And long-term global climate change promises to make that task even more challenging.
"The VRN-D4 gene and the other three vernalization genes can be used by plant breeders to modify vernalization requirements as they work to develop wheat varieties that are better adapted to different regions or changing environments," Kippes said.