Wheat truly feeds our world. It accounts for a full 20% of the calories we consume, and 35% of the planet’s population depends on it for their very survival.
Yet the crop has remained relatively elusive to scientists, partially due to its complexity at the genetic level. The wheat genome has about 17 billion paired DNA bases, which makes this grain crop even more complex than the human genome. And because about 80% of the genome contains repetitive sequences, it has been difficult to interpret readouts because of the challenge in knowing whether a particular sequence is unique or a repeat.
But a recent scientific breakthrough has allowed an international team of scientists to complete a shotgun sequencing of the wheat genome. This process breaks up the genome into smaller, more workable segments for easier analysis.
Shahryar Kianian, professor of plant sciences at North Dakota State University and one of the project’s collaborators, says the project has been in motion for several years. Generating the necessary information was a fast, relatively inexpensive process, he says—but assembling and arranging this information required quite a bit of brainpower and computer processing.
"Essentially, we put together the world’s largest jigsaw puzzle," he says.
Why go through all of the trouble, then? Researchers hope the study will lead to multiple positive outcomes. For example, the sequencing project greatly multiplied the number of available genetic markers for plant breeders to use, Kianian says. That knowledge could be used to more effectively breed and adapt wheat to parts of Asia and sub-Saharan Africa to improve drought tolerance, or create varieties that are more resistant to devastating diseases.
"Fifteen years ago, we had about a thousand markers," he says. "This breakthrough put us in the millions. Now, if you are targeting UG-99 resistance, for instance, you can transfer genes more easily and more cleanly."
Researchers say there is still much work to be done. Bikram Gill, Kansas State University distinguished professor of plant pathology and director of the university’s Wheat Genetics Resource Center, says the next step is to develop a "gold standard sequence" for wheat. For this project, scientists will anchor the complete sequence to a genetic map of agronomic traits important to the wheat industry.
Researchers at WGGRC and elsewhere are also carefully studying the wheat’s polyploid properties, which could lead to additional breakthroughs in other food crops such as cabbage and broccoli.
"The polyploidy is both a curse and a blessing," Gill says. "It provided the evolutionary novelty that made wheat the world’s most important crop, but at the same time, it made the genome more complex and a hard nut to crack."
For now, the gene sequencing has allowed researchers to identify, categorize and record individual genes and gene cluster locations. Gill considers it a rough map but one loaded with points of interest for future studies. Like his collaborators, Gill is still focusing on the true prize—the gold standard sequencing.
"With funding from the USDA and the National Science Foundation, center scientists have made sequence-ready physical maps," he says. "But lack of funding is hurting the U.S. effort for gold standard sequencing of the wheat genome."