Experts summon blessings from wheat’s ancient past

Reaching into the annals of wheat history, breeders of the staple crop from several states are finding solutions to modern problems.

Persistent drought and other threats to wheat production on the High Plains have sparked collaborations from researchers at Kansas State University, Colorado State University, and the U.S. Department of Agriculture’s Agricultural Research Service in both areas.

Transferring genes from the grain’s “ancient relatives,” may be the key to producing a more drought-tolerant wheat, said Allan Fritz, Ph.D., K-State wheat breeder.

Traveling in reverse through the crop’s evolution, when wheat’s parents were considered weeds, scientists are latching onto traits that could infuse modern varieties with more drought tolerance.

Others are on the trail of a pest dubbed wheat stem sawfly that is devastating fields from spring wheat country in Montana now migrating to northeastern Colorado and the Nebraska panhandle.

“We’re now going back and finding what was good that we missed,” Fritz said. “It’s like sorting through a garbage pail, but there are some real gems in there.”

Joining forces with Geoff Morris, Ph.D., associate professor of crop genetics at CSU, they are searching for drought tolerance from Aegilops tauschii, an ancestral goat grass, and Triticum dicoccoides, commonly known as wild emmer.

Cereal connection

Selections of these ancestral relatives come from the center of origin of cereal crops, the Fertile Crescent found in the Middle East, Morris said.

Punya NaChappa, Ph.D., associate professor of entomology at CSU, and Mary Guttierri, Ph.D., hard winter wheat research geneticist for the USDA Agricultural Research Service, are also looking at wild emmer as a source of resistance to wheat stem sawfly.

“They are natives to some really dry and hot environments,” Fritz said. “We think there are sources of genes that will do well in harsh conditions in Kansas and the Great Plains. From a production standpoint, 2022 wasn’t a great year.”

Wheat and other crops need ways to combat the bone-dry conditions that persist in the High Plains.

“Colorado State and K-State plots near Hays, (Kansas), have some really nice products, but you still need good genetics to help you,” he said. “We need to find those and put them into the background that breeders can use—mobilize diversity from the wild relatives into adaptive germ plasm or adaptive materials.”

Researchers are able to latch onto the desired genes from wild wheats.

“This is really novel stuff,” Morris said. “The trick they use in this project is to move wild genes into the latest and greatest elite varieties. Now it’s much easier for us to find out which wild genes will help modern wheat.”

Morris likened it to taking the best automobile technology from an off-road racing program and putting it into the development of pickup truck lines, where it will be useful to the consumer.

Shortening the wait

In essence, the scientists are able to shorten the wait from identifying genetic traits, “moving traits into the breeding programs and then on to the farmers’ fields,” he said. “With these wild genes inside modern wheat varieties, we’re doing our testing in material that is close to the end product. It hugely speeds up the process.”

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In some cases, the wild wheat’s answer for drought is dormancy “by not growing, which is not useful,” he said. “But the wild wheat may have a chemical compound that helps the plant stay healthy when it’s under drought conditions, and that’s something we can use in a modern wheat breeding program.”

Fritz and Guttieri agree the place to run a drought study for wheat is at the USDA-ARS Limited Irrigation Research Facility near Greeley, Colorado, not at K-State’s research farm near Colby.

“I told the (Kansas Wheat Commission) if they funded a drought study in Colby, we’d never have a drought. Every time I have a drought study there, it rains a lot,” Fritz said.

Sadly for Greeley, drought is more reliable there, Guttieri said.

“They have a drip system to apply irrigation very precisely and manage that drought stress,” she said. “It is able to apply enough irrigation water before we plant to get it out of the ground, and then manage the severity of the drought stress through the growing season. This is a really great field site for doing drought research.”

Wild emmer

Wild emmer is the ancestor to modern day durum wheats, she said.

“About 10,000 years ago, wild emmer was domesticated. Aegilops tauschii and a domesticated emmer, combined to produce a hexaploid wheat, which has the A, B, and D genomes. We call that a polyploidization event,” she said. “Emmer has the A and B genomes and Aegilops tauschii has the D genome.”

The hexaploid bread wheat occurred naturally a very limited number of times in the wild, and contains three sets of seven chromosomes each.

“We can make these kinds of things in the greenhouse and lab now, but it’s technically difficult, so it was really quite miraculous that it happened,” Guttieri said. “These very primitive wheats started inter-mating with their ancestors and with each other. Mutation for a free-threshing characteristic occurred, and the earliest of wheat farmers selected and propagated increasingly domesticated plants; what we would call landrace wheat. That means that they were likely selected for domestication traits.”

Wild emmer and Aegilops tauschii don’t thresh out and shatter at maturity.

“The earliest plant breeders started selecting for plant types where the seed remained in the spike until it was harvested, and the seed could be readily rubbed out,” she said. “The end results of this evolutionary history is that because the durum ancestor and the D genome ancestor combined so rarely, that a lot of the genetic variability has never been brought forward into modern wheat.”

Guttieri referred to the development as being caught in a “giant bottleneck, and very few joined for the polyploidization, leaving behind a lot of good stuff. Plant breeders prior to Allan and I realized it was there.”

Leaf rust resistance, too

The Wheat Genetics Resource Center at K-State has found leaf rust resistance from Aegilops tauschii, she said, and other scientists have introduced stripe rust resistance from wild emmer.

Another bonus from Aegilops tauschii is Hessian fly and wheat curl mite resistance. Wheat curl mites carry the devastating wheat streak mosaic virus.

“All of these efforts have been targeted to very specific traits, something where one gene can make a tremendous difference,” Guttieri said.

Wheat stem sawfly, an “endemic pest” of northern spring sheet regions, has moved to the Nebraska panhandle and northeastern Colorado. Having one lifecycle, the sawfly lays its eggs in the upper part of the wheat stem, and the larvae eat the stem from the inside out.

“You have this beautiful field of wheat, then a wind comes through, and the field looks like it has been rolled, layed down. It happens early enough that seed don’t fill very well. It’s devastating,” she said.

In cooperation with Colorado State, Guttieri’s germ plasm bred from wild emmer, and germ plasm Fritz bred from Aegilops tauschii, is being evaluated in northeastern Colorado under sawfly pressure.

“Because this terrible insect only has one cycle a year, it’s really impossible to control it with insecticide, and there has been limited success with biological control, with things that parasitize the sawfly,” she said.

Pulling germplasm from history has produced some hope.

“We have been finding some promising levels of resistance to sawfly in this germ plasm that we’re very excited about,” Guttieri said. “We have begun making crosses into the solid stem wheat germ plasm that is presently used to manage the sawfly. Essentially, we’ve started breeding for it.”

Sawfly work is in cooperation with Esten Mason, Ph.D., the CSU wheat breeder.

“It’s really a joy to work in wheat on the Great Plains. It’s a very collaborative research community,” she said, “and there’s always something to learn form the past, and we’re reaching pretty far into the past, like 10,000 years.”

Tim Unruh can be reached at [email protected].