Doubled-haploids hasten barley, wheat development for Northwest farmers
By John O’Connell
The American Malting Barley Association now has only two recommended winter malt barley varieties, drastically limiting the options of growers. But a new cross of those varieties, called 10.0777, may soon provide growers with a powerful new option that offers the best attributes of each.
And thanks to an innovative laboratory shortcut, that hybrid will be available years ahead of the normal breeding timeline. Called doubled haploid technology, it is part of a scientific trend that is bringing new barley and wheat hybrids to market in the Pacific Northwest faster than ever before.
Pat Hayes, a barley breeder at Oregon State University, explained that 10.0777, crossed four years ago, is a doubled haploid. That means it was bred with two identical sets of genes — haploids — to avoid variation among the progeny. The technology fast-forwards breeding by years without introducing foreign genes, as is done with controversial genetically modified organisms.
Hayes said 10.0777, which would still be in development without doubled haploids, is “planted all over the Pacific Northwest and in the AMBA qualifying trial.”
Now the method of choice for breeding corn and some other crops, doubled haploid technology has existed for decades but has seen expanded use in recent years. In wheat and barley, public and private breeding programs alike are increasingly contracting with doubled haploid laboratories to speed up their work. Still others are implementing the technology themselves.
Hayes first dabbled in doubled haploids about 25 years ago, using a less efficient method, but abandoned the practice when it didn’t pencil out economically. He resumed doubled haploid production in the spring of 2012 with a $10,000 AMBA grant. His laboratory now has contracts to make doubled haploids for seven other barley programs — including Washington State University’s and the USDA’s Agricultural Research Service in Aberdeen, Idaho — and should become self-sufficient by July. He charges $35 per doubled haploid plant.
How it works
The traditional approach to barley breeding involves fertilizing the egg of one parent plant with the pollen of another and self-pollinating the progeny that best express the desirable characteristics of both.
Genetic variation is cut in half with each subsequent self-pollinated generation. After about five generations, the plants breed true, meaning other gene combinations are mostly gone and progeny consistently have the best attributes of both parents.
After making a cross in his doubled haploid program, Hayes places an anther from the best first-generation plant into a special medium. With a regimen of nutrients and hormones, his medium “tricks” pollen grains from the anther into generating a plant in the absence of an egg. The resulting doubled haploid plants simply replicate the single gene strand in the pollen to produce a second set of identical genes, thereby avoiding the need to breed out variability in subsequent generations.
“We’re not messing with the underlying genetic content that’s there,” Hayes said. “We’re just getting new combinations of genes, and they would have occurred naturally if you went through enough cycles of self-pollination.”
To date, OSU’s internal program has generated 5,200 doubled haploid lines from 320 crosses, both for malting and food barley development, said Assistant Professor Alfonso Cuesta-Marcos. OSU has made 500 other lines for customers.
“Our projection for 2014-2015 is that we will generate approximately 5,000 doubled haploid lines, of which 3,500 will be for the OSU barley breeding program and 1,500 for external customers,” Cuesta-Marcos said. “We have not released any (doubled haploid) variety yet, but we have a good set of potential varieties in preliminary yield trials.”
Pursuing a new winter barley
Improved methods used to make doubled haploids have reduced the cost of the technology. It’s beginning to make economic sense in barley breeding, explained Scott Heisel, AMBA vice president and technical director.
He said the technology has been especially useful in the effort to develop badly needed new winter malt barley varieties. Breeders pursuing spring varieties can plant extra generations in greenhouses or warm winter climates. Shortcuts are limited for winter barleys, which must be exposed to winter growing conditions.
Gonghse Hu, barley breeder at the Aberdeen, Idaho, Agricultural Research Service facility, hired Hayes last October to produce 1,000 doubled haploid families from crosses made in his laboratory. All of them will be 2-row winter malt varieties. When the first doubled haploid plants are sent back to Hu for field trials, he’ll seek improved winter hardiness and malting quality.
“For winter barley, doubled haploid can reduce three to four years. That’s significant,” said Hu, who now utilizes doubled haploids in about 5 percent of his breeding program. He also hopes to expand his use of doubled haploids and to further expedite breeding with genomics — selections based on genetic markers associated with certain traits.
Idaho Barley Commission Administrator Kelly Olson considers the combination of genomic selection and doubled haploids to be “the cutting edge of breeding techniques today.”
“In barley we’ve struggled to keep up because we haven’t seen this huge influx of private-sector dollars like we have in corn and soy, and now in wheat,” Olson said. “The exciting thing for barley’s story is we, too, have the ability to utilize these technologies, and we are — maybe at a smaller scale.”
Speeding up wheat breeding
As a research associate and Ph.D. student at Virginia Tech University, Jianli Chen bred doubled haploid wheat through a common method utilizing corn pollen.
Scientists first remove the anthers from a wheat plant resulting from the cross of two desirable parents. Eggs of the emasculated plant are then fertilized with corn pollen, stimulating embryo development. Corn and wheat are too dissimilar for any of the corn genetics to remain throughout embryo development. The developing embryo is then removed and placed in a medium with hormones and nutrients, causing it to continue growing into a plant with a single set of genes. By applying a chemical, scientists cause the plant to make exact duplicates of its chromosomes, creating a doubled haploid plant.
Chen continued utilizing the approach in 2008, after taking a position as wheat breeder with the University of Idaho’s Aberdeen Research and Extension Center. One of her initial doubled haploid crosses, the soft white winter wheat IDO 1108, entered regional planting trials in 2012. It has good resistance to the fungal diseases stripe rust and dwarf bunt, good end-use qualities and posts strong yields, Chen said.
“If we had gone through the normal process, this year would be the first year of yield trials,” Chen said. “I think we saved three to five years.”
Doubled haploid breeding ultimately proved too costly for Chen to continue. She now hires a private company in Kansas, Heartland Plant Innovations, to create her doubled haploids. Chen eventually plans to utilize doubled haploids in at least half of her hard white wheat breeding.
WSU started its doubled haploid wheat breeding laboratory in late 2009 with financial help from the Washington Grain Commission. WSU continues to breed doubled haploid wheat and has made its program self-sufficient by doing paid work for programs at Colorado State University and North Dakota State University. WSU uses genomic analysis to further expedite the breeding process.
WSU wheat breeder Arron Carter said the program now has its first doubled haploid lines in statewide variety testing, with its initial breeding emphasis on plants with multiple genes that offer stripe rust resistance. Though WSU utilizes the corn embryo breeding method, Carter explained his laboratory is working to perfect a process with microspores — making a doubled haploid exclusively from wheat pollen, as Hayes does in his barley lab. In a few years, Carter anticipates microspores will become the preferred method in doubled haploid wheat, as well.
“Most winter wheat breeding programs are starting to look at doubled haploids. If they haven’t fully converted, at least they’re starting to make a few crosses to evaluate how it will be useful to their program,” Carter said.