Hybridized wheat: 7 years in the making

One researcher is in Texas. One is in Nebraska. Together, they are striving to launch the hybridized wheat industry.

Hybridization is the cross breeding of two genetically different varieties or species. And much like what has been accomplished in cotton and corn, hybridizing wheat is expected to improve the crop’s strength and health and ability to feed a rapidly growing population.

Amir Ibrahim, Ph.D., Texas A&M AgriLife Research wheat breeder in Texas A&M’s Department of Soil and Crop Sciences, Bryan-College Station, has spent the past seven years studying the hybridization of wheat in a partnership with Stephen Baenziger, Ph.D., University of Nebraska-Lincoln small grains breeder.

Ibrahim and Baenziger jointly have tested more than 600 lines of hybrid wheat varieties in Nebraska and Texas, and are now developing the necessary knowledge base, germplasm and enhanced trait pools or patterns from these lines to support the development of hybridized wheat.

Plant breeding partnerships grant

The team’s newest project, “Plant breeding partnerships: Continuing to develop and validate the tools for hybrid wheat,” is supported by a $650,000 U.S. Department of Agriculture National Institute of Food and Agriculture grant.

“Together our project team has made great strides toward developing tools to foster hybrid wheat development to maximize wheat yield potential,” Baenziger said. “This project is expected to help create the scientific and germplasm foundations for successfully launching a U.S. hybrid wheat industry.”

Using an integrated approach involving in-house germplasm, chemical hybridizing agents, breeding, phenotyping, genomic selection and quantitative trait loci mapping, the collaboration’s objectives are to:

            – Validate increased function from previously made and predicted wheat hybrids in replicated trials.
– Continue male and female parent line evaluation for characteristics needed to develop experimental and commercial wheat hybrids in a cost-efficient manner.
            – Develop those groups showing enhanced traits or patterns and test multiple mating designs for wheat hybrids.
            – Continue cytoplasmic male sterility line development and identify and validate restorer genes for wheat hybrids.

Why hybrid?

Ibrahim explained hybrid crops have increased vigor over the two parents in yield and other traits. In hybrids, the female parent does not produce viable pollen, but is used as a seed plant. The male parent has the role of pollinator. Together they have the capacity to combine and express hybrid vigor.

For wheat, past conventional breeding efforts increased hybrid vigor about 10%, but Ibrahim said they want to raise that figure to 15%-20% to make it attractive to producers.

“We believe hybrid wheat, which is more climate resilient than pure-line wheat, can contribute to achieving this goal,” he said.

Also participating in this latest project are Vikas Belamkar, Ph.D., University of Nebraska geneticist and plant breeder; Bhoja Basnet, Ph.D., International Maize and Wheat Improvement Center, or CIMMYT, hybrid wheat breeder, El Batan, Mexico; and Jochen Reif, Ph.D., Leibniz Institute of Plant Genetics and Crop Plant Science department head, Gatersleben, Germany.

The science needed for cost-effective adoption

Anil Adhikari, Ph.D., a Texas A&M doctoral student who is now at the University of Wisconsin, said for commercial success of hybrid wheat, a cost-effective hybrid seed production method is required. Adhikari worked extensively with Ibrahim on the genetic side of hybridization.

Hybrid seed production based on cytoplasmic male sterility is only feasible if the male lines have fertility-restoring genes, Adhikari said. These genes override the cytoplasmic male sterility in the hybrid seed and make the seeds fertile.

In his study, fertility-restoring genes in a promising restoration source were mapped using linkage mapping approach in a population of 300 recombinant inbred lines. Three consistent major quantitative trait loci, or QTLs,were mapped explaining 18%-40% phenotypic variance. KASP markers were developed using flanking markers of these QTLs.

The KASP markers from this study can be used for characterizing fertility-restoring gene sources and transferring them to male parents in the hybrid breeding program. In addition, the identified candidate genes can serve as a guide to fine map and clone these fertility-restoring genes.

The time has come

To meet population and food projections, the improvement in wheat productivity needs to be between 1.4% and 1.6% per year. Currently, the productivity increase is about 1% or less.

The researchers say we now have effective chemical hybridizing agents to make experimental hybrids, have identified lines with good traits to facilitate cross-pollination, genomic tools for predicting hybrid vigor, statistical approaches for better estimates of hybrid yield in large experiments, and genomic tools for better use of cytoplasmic male sterile systems.

Hybrid wheat appears to be more stable than conventional wheat under stresses, a trait that is growing in importance, Ibrahim said. Also, he knows the research spin-offs from these efforts may have far-reaching improvements for his and other wheat breeders’ conventional pure-line breeding.

“We know hybrid wheat will still take time but based on these tools we have been working with and the results we are seeing, we believe its time has come,” Ibrahim said.