A new wheat variety blends familiar genetics with fresh resistance and agronomic traits — but emerging pathogens raise new questions.
Stripe rust and leaf rust continue to pressure wheat growers across the Southern Plains, with shifting pathogen populations and unpredictable infection timing threatening both yield and grain quality.
As growers weigh fungicide costs, disease timing and variety resistance, researchers are working to develop cultivars that offer broader protection and stronger agronomic performance.
Oklahoma State University’s latest Clearfield wheat release, Orange Blossom CL+, enters the landscape with a familiar genetic base — and a few new traits aimed squarely at today’s rust-related risks. The release follows years of internal development and field trials. The variety features a familiar genetic backbone and brings a combination of higher yield, early stripe rust resistance, and test weight comparable to its predecessor, Doublestop CL Plus.
Building on a Trusted Foundation
Brett Carver, OSU wheat genetics chair and regents professor, says the decision to build on Doublestop CL Plus genetics was intentional.
Brett Carver, OSU Ferguson College of Agriculture wheat genetics chair and regents professor. (Photo by Mitchell Alcala/OSU Agriculture)
“Genetically speaking, we stayed close to home with Doublestop CL Plus when breeding Orange Blossom CL Plus,” he says. “These two varieties share about 66% of their genes in common. Thus, we could really focus on grain yield and disease resistance with the confidence of knowing we had a strong foundation.”
According to Carver, Orange Blossom CL+ is likely one of the last Clearfield varieties developed at OSU using a closed-loop breeding system, where all parents carried two-gene CL Plus herbicide tolerance.
“This allowed me to ratchet up selection pressure for grain yield with the assurance we would not sacrifice past gains in key traits like herbicide tolerance,” he says.
Early Stripe Rust Resistance Expands Protection Window
The stripe rust resistance package is a notable feature, with protection appearing earlier than in most wheat varieties grown in the region.
“Stripe rust resistance in Southern and Central Plains wheat varieties is largely of the ‘adult-plant’ kind, which does not usually kick in until after anthesis or flowering,” Carver says. “In some years, that’s enough — but in years like 2024 and 2021, we needed protection earlier in crop development to have a better chance of realizing yield potential.”
Orange Blossom wheat growing at Oklahoma State University. (Photo by Mitchell Alcala/OSU Agriculture)
This earlier resistance could offer an advantage for growers in seasons with high early disease pressure, particularly when fungicide use is limited.
Evolving Leaf Rust Pathogens Prompt New Breeding Strategies
Data from the 2023–2024 growing season also highlighted new challenges. Carver, who was recently named Big 12 Faculty Member of the Year, and his team observed reactions to leaf rust in Orange Blossom CL+ that suggest emerging pathogen races are shifting the resistance landscape.
“We already knew this, but the leaf rust reaction we saw on Orange Blossom CL+ late in the 2023–2024 season provided a stark reminder of the importance of deepening and broadening our leaf rust packages moving forward,” Carver says. “For leaf rust, we have to add more stuff to the stew by combining different kinds of resistance into each variety, such as all-season resistance and adult-plant resistance.”
That ongoing effort is led by OSU wheat pathologist Meriem Aoun.
OSU wheat pathologist Meriem Aoun leads the ongoing efforts to combat rust in wheat. (Photo by Mitchell Alcala/OSU Agriculture)
“Orange Blossom CL+ is resistant to prevalent leaf rust pathogen races in Oklahoma. Based on molecular markers, Orange Blossom CL+ does not carry any of the known leaf rust resistance genes commonly deployed in hard winter wheat grown in the US Great Plains,” she says. “We are quickly working to identify and characterize the novel leaf rust and stripe rust resistance genes in this cultivar.”
Deeper Planting Flexibility Emerges After Release
Carver says the variety also showed deeper planting ability, which may be useful in drier planting windows. This trait, identified after the initial release, is linked to a longer coleoptile.
“The deeper planting ability of Orange Blossom CL Plus stems from its longer coleoptile, which can be an asset in either [grain-only or dual-purpose] system,” Carver says. “We did not know this important fitness characteristic until after its release, and we credit our wheat extension specialist Amanda Silva for discovering it.”
Carver emphasizes that planting flexibility could benefit producers working in dual-purpose grazing and grain systems by increasing access to soil moisture during fall droughts.
“Broader fitness allows wheat producers greater freedom to operate,” he adds.
Quality Profile Suited for Commodity Blending
When it comes to quality, Carver says Orange Blossom CL+ has above-average milling characteristics, while baking performance is described as average.
“Its quality profile is well fit for a commodity system where varieties of varying functionalities are blended,” Carver says. “Orange Blossom CL Plus will certainly raise the value of the blend for test weight and protein but may need help from other varieties with greater dough strength.”
New Research Facilities to Support Breeding Innovation
Looking ahead, the OSU Wheat Improvement Team is preparing to expand research capacity with the proposed Agronomy Discovery Center in Stillwater. The facility will include new greenhouses and lab space for multiple research teams, including wheat quality and pathology.
“In short, the Agronomy Discovery Center will allow the wheat improvement team to intensify its breeding efforts with access to more breeding tools and allow us to expand our operation by utilizing a greater portion of the calendar,” Carver says. “We’ll be able to shift financial resources from protection of the breeding program to innovation within the program. We believe the latter will have greater direct impact on our wheat industry.”
The variety’s name is a play on the famous 1930s fast-paced musical piece “Orange Blossom Special” by Ervin T. Rouse. The song was primarily played on the fiddle and uses double stops, a musical technique of playing two notes simultaneously on a stringed instrument. Orange Blossom CL+ is available in limited supply through OSU Foundation Seed Stocks, with broader commercial availability expected to follow.