Kansas State University researchers unlock secrets of heat tolerance
A bit of rice in the wheat? Aiming for greater heat-tolerance, Harold Trick and Allan Fritz shot a rice gene into wheat and might have hit dead-center—smashing open a window to increased yields and greater profits for farmers.
The Kansas State University (KSU) research duo is looking at different traits that allow wheat to survive high temperatures. Soluble starch synthase (SSS), a key protein involved in grain fill of wheat seed, converts sugars to starch. Wheat normally likes optimum temperatures—60°F to 65°F during the grain-filling process—a temperature range where SSS functions best. With high temperatures, the protein deactivates.
“It’s the equivalent of an engine overheating and seizing up,” says Trick, a plant pathologist.
For every couple of degrees above the optimum temperature, wheat loses 3% to 4% of yield potential. In Kansas, wheat seed normally begins to fill in late May or early June. During this time period, temperatures in the Great Plains can often jump into the 90s—and those spikes can wreak havoc on wheat.
“If you look at the Great Plains where we have 40 bu. to 45 bu. per acre wheat, as opposed to the Pacific Northwest where they grow 120 bu. per acre wheat, what’s the difference?” asks Fritz, a wheat breeder. “Sure, some of it is moisture, but a lot of it is temperature. They have an eight-week period to fill grain, but we’re dealing with 25 to 28 days to fill grain.”
Is there a step-change for wheat yield in warmer environments? If there is one, it’s going to include some level of heat-tolerance improvement, which would quickly bring a bump in yield. Trick and Fritz looked for a protein from an outside plant source and quickly focused on rice, a closely related cereal crop that thrives in warm temperatures. They isolated the gene that codes for the heat-tolerant trait in rice, and through genetic engineering (GE), placed the gene in wheat. Basically, the wheat has two copies of the protein—wheat and rice versions.
In testing, their transgenic wheat was exposed to daytime temperatures at 93°F and nighttime temperatures at 82°F.
“We allowed the plant to fully mature at those temperatures,” Trick says. “We looked at the non-GE versions versus the GE versions and saw a 34% increase in the weight of the seeds—a tremendous difference for the GE version. That difference could translate into millions of dollars for U.S. farmers.”
Their transgenic wheat won’t produce a blanket 30% yield boost. When temperatures are normal, the new gene doesn’t produce any benefit. However, when extreme temperatures arrive, the gene kicks in, stabilizing the yield load. Achieving heat tolerance in a plant involves a number of factors, and their breakthrough isn’t a cure-all for problems related to water and drought-resistance. Trick and Fritz hope to take their introduced trait and combine it with other heat-tolerant wheat varieties through classical breeding.
“None of this research would have been possible without Kansas wheat producers and grants through the Kansas Wheat Commission,” Trick says. “They’ve been very supportive of our program.”
The next phase of research will focus on determining how high temperatures will affect wheat in a real-world field environment. Regardless of how much promise the new wheat trait shows in trials, there are still many market obstacles that remain. Opposition by consumers and trading partners to transgenic wheat is a concern, the researchers say.
“We’re going to have GE wheat, but I don’t know about the time frame,” Fritz predicts. “I don’t know if we can forfeit 15% of our crop because we refuse to use GE wheat. It’s hard to ignore the value of these traits.”
Getting GE products to market takes millions of investment dollars toward testing, and the KSU
researchers are looking for industry partners.
“We simply want to eliminate obstacles in order to achieve a safer, more affordable food supply,” Fritz says. “Heat-tolerance is one piece of the puzzle in removing barriers to yield and productivity.”