The USDA-ARS research center at Stillwater, Okla., has become the go-to place for insect resistance work on grain sorghum, wheat and barley.
USDA plant breeders are identifying plant resistance for greenbug, Russian wheat aphid, chinch bug and sorghum midge.
“We focus on sorghum and cereal crops,” says Dave Porter, research leader at the Stillwater unit. “This is the only program in the country doing this type of work at this level and for the entire industry.”
He says Stillwater is the center for insect resistance work in sorghum and cereals.
Plant breeder Yinghua Huang works on sorghum and Do Mornhinweg concentrates on barley, while Dave Porter works on wheat.
“We've been fortunate to get research funding from the National Sorghum Producers for a new program at Stillwater,” Huang says. “This is the lone program addressing insect resistance in sorghum.”
Huang works with both molecular genetics and classic breeding. “We use molecular genetics to identify greenbug-resistance genes, cross breeding to move them into cultivars, and marker-assisted selection (MAS) to facilitate the breeding process. We began moving resistant material into the same sorghum varieties farmers would plant to meet production requirements. To date, several resistant lines have been created and are at the F4 and F5 stages.”
He evaluates plants in the greenhouse and in the field. “In all, we have four stages of evaluations from the greenhouse through field studies.”
Huang says the screening process includes evaluations at the three-leaf stage (about seven days) then at 14 days and finally at 21 days. “Only a few good ones survive 21 days with insect infestations,” he says.
“Our ultimate goal is to develop sorghum varieties with high performance and greater resistance to greenbug, chinch bug and sorghum midge. Greenbug is the primary focus.”
Huang said initial screening included 42,000 germplasm lines. “We identified more than 26 resistant sources. Now, we face the challenge of determining the genetic mechanism for resistance. We have to understand the genomic structure for resistance and how the resistance works.”
He says diversity in resistance is crucial. “New biotypes of greenbug develop quickly to overcome plant resistance, so we want to include multiple resistance mechanisms in order to install a durable resistance as a long-term solution to the greenbug problem.”
Porter says NSP support is key to accomplishing Huang's goals. “We can do more germplasm characterization and screening,” he says.
“We also enjoy a good relationship between public and private breeding programs,” Huang says. “We work with Pioneer to evaluate their breeding material. We also work with USDA labs in Lubbock, Texas, and Lincoln, Neb.”
Huang says in addition to resistance work he's trying to identify high yielding sorghum lines for use in ethanol production.
Mornhinweg screens barley lines looking for resistance, primarily to Russian wheat aphid. We identified several sources of resistance and immediately released two unadapted germplasm lines for breeders to work with,” she says. “Since these early releases were not adapted to U.S. barley production areas, we began a backcrossing program to develop adapted resistant germplasm lines for U.S. breeders.”
She says research includes “every type of barley (winter, spring, malt, feed, two-row and six-row) aiming to get resistance into the best materials for every state. She's also concerned with genetic diversity. “We have new biotypes of Russian wheat aphid and we're watchful for new biotypes of greenbug. We need to identify different genes and utilize them all to assure resistance.”
Varieties also have to measure up to grower production standards. “We are confident that what we release will do well in the field,” Mornhinweg says.
She has one co-release, Burton Barley, named for long-time Stillwater ARS scientist Robert Burton, who coordinated much of the initial insect research efforts for ARS.
“Burton is the first RWA resistant barley cultivar in the United States,” Porter says. “It may be the first in the world.” Two other RWA resistant feed barley cultivars have been approved for release with more coming in the future. All of these releases are cooperative efforts with other USDA-ARS units as well as state breeders.
Porter says the barley industry, including the American Malting Barley Association and the National Barley Improvement Committee, as well as state breeders, “look to Stillwater for resistance efforts.”
He says work on Russian wheat aphid is especially important. “It's been in the area for 20 years. Distribution is sporadic in some locations, showing up only occasionally while in other areas, it occurs every year.”
The Russian wheat aphid infests grain in Texas, Oklahoma, Nebraska, Colorado and farther north and west, he says, and can be devastating.
“Some areas can't afford insecticide treatments (with limited yield potential) so they need resistance,” Morninweg says. “Farmers in those areas are clamoring for it.”
She's also developing a winter hulless barley for Oklahoma that can be used for ethanol and will be RWA and greenbug resistant as well.
“Developers are building an ethanol plant north of Stillwater,” Porter says. “Barley will be a highly valued crop for the plant because of the high value of the distillers grain.”
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