Texas, USA
March 1, 2016
There’s growing interest in hybrid wheat and Amir Ibrahim, a Texas A&M AgriLife Research wheat breeder in College Station, believes the time is right to make it available.
Ibrahim has been working toward the development of hybrid wheat varieties since 2013, but wheat breeders first began looking at hybridization in wheat more than 50 years ago in the early 1960s, he said.
“The price for wheat was so low, and the cost for the hybrid seed was too high at the time,” he said. “Today we have a better handle on the genes and better prices and availability of genomic tools.”
And it is something that is needed, Ibrahim said. Wheat production yield potential has been leveling off and “this is one way to break that barrier.”
The performance of the TAM varieties of wheat developed by AgriLife Research’s wheat breeding team has been improving across the state and into other states with diverse climates, providing a solid base of germplasm.
Under a Monocot Improvement Initiative grant by AgriLife Research, as well as funding from the Texas Wheat Producers Board, Ibrahim is working with the University of Nebraska-Lincoln to test more than 600 lines of hybrid wheat in Nebraska and Texas.
Ibrahim explained U.S. corn is a hybrid crop. The hybrid crops have increased vigor over the two parents in yield and other traits. There must be enough hybrid vigor, technically referred to as heterosis, to justify the increased costs of seed and production.
For wheat, past efforts have increased hybrid vigor about 10 percent, but Ibrahim said they want to get that figure in the range of 15-20 percent to make it attractive to producers.
He explained hybrid seed must be bought each year due to inbreeding depression and dilution of vigor associated with growing saved seed, so producers cannot save their seed and replant, as is commonly done now.
In hybrids, the female parent does not produce viable pollen, but is used as a seed plant, Ibrahim said. The male parent has the role of pollinator. Together they have the capacity to combine and express hybrid vigor.
Part of the problem has been the increased cost of seed. There are two systems for producing seed: chemical hybridization agents, which kill the anthers on the female; and the male sterility system, which includes breeding females and males separately and making selections based on the best combination.
The effort now is aimed at developing cytoplasmic male sterile females and male parents by breeding fertility restoration genes into them, he said. A minimum of three fertility restoration genes is needed in the males. This genetic system is very slow.
Hence, AgriLife Research and University of Nebraska-Lincoln are working on developing parents using a chemical system for suppressing pollen development in the females, Ibrahim said.
He said this does not require breeding male sterile genes in the female and restoration genes in the male pools, although both approaches are utilized in Ibrahim’s program.
“For successful hybrids, parents need to be genetically distant to maximize hybrid vigor, and that’s why AgriLife Research is collaborating with UNL, as the two institutions have divergent germplasm,” Ibrahim said. “If you cross same to same, you don’t get the hybrid vigor.”
He said they will continue to try new combinations every year and then will need to test the hybrids for several more years before anything is released.
“Within five years, I hope we can have the first commercially available hybrid seed available for producers,” Ibrahim said.
He said in addition to the field work, his team now has access to medium- to high-throughput genotyping, which will help them map the restoration genes and understand hybrid vigor at the molecular level. They are also screening the germplasm for the floral characteristics and for combining ability.
With the next generation sequencing technology, Ibrahim said they may be able to select for performance traits that can result in higher biomass and yield, drought tolerance, consistent performance, quality, disease resistance and agronomic adaptation, vigorous root system and increased production in low-fertility conditions.
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