It Ain’t Easy Being a Sunflower Breeder
Growers want sunflower hybrids with high yield and high oil, excellent standability, pest resistance, and market versatility, at the best price possible. Processors and end users want hybrids that result in seed at a specific size and oil content, at the best price possible. Meanwhile, company brass and stockholders want hybrids that sell – at the best price possible.
No, it ain’t easy being a sunflower breeder.
Yet consider the advancements that have been made in recent years, including an entire new oleic category (NuSun™) imazamax-resistant sunflower (Beyond™, for use on Clearfield™ sunflower hybrids), strides in oil and yield (there are reports this year of 3,000 lb dryland yields in the Northern Plains) and sunflower germplasm with better disease tolerance, a trait that can be found in a number of new hybrids coming into the marketplace now.
Much of the disease resistant germplasm base that companies use to develop hybrids comes from the USDA-ARS Red River Valley Agricultural Research Center in Fargo, N.D. Comprising a professional research staff of about a dozen, this is the only federally-funded Sunflower Research Unit in the country, although cooperative research is also conducted at a number of land-grant universities, mostly in sunflower-producing states.
This basic research includes finding, incorporating, and evaluating genes in wild and cultivated sunflower from across the world. After thorough evaluation over multiple years and growing environments, sunflower germplasm is released by the USDA-ARS to the public for commercialization. Seed companies use the germplasm made available by ARS to breed improved hybrids – to analogize, USDA’s basic research is the lumber (germplasm or parent lines) from which seed companies build houses (hybrids) to sell to consumers (growers).
USDA-ARS research geneticist Jerry Miller has been at the forefront of sunflower germplasm development over the years, including NuSun and Clearfield sunflower. The coup de grâce of Miller’s sunflower research career, however, would be the development of Sclerotinia-tolerant sunflower hybrids. “We’re getting closer,” says Miller. “The genes and the basis for better genetic material are there.”
An emphasis on Sclerotinia tolerance has been a primary sunflower breeding objective in recent years, particularly after the 1999 disease epidemic in the Northern Plains. “Every line we produce now is screened for stalk and head rot,” says Miller. Sclerotinia research in sunflower is funded in part by the NSA, as well as the National Sclerotinia Research Initiative (www.whitemoldresearch.com).
Now, there are noticeable differences both in existing hybrids and upcoming lines in terms of resistance to both stalk and head rot. But developing Sclerotinia-tolerant germplasm is just one piece of the puzzle. For example, a line out of Chile or China might offer an excellent source for natural genetic Sclerotinia tolerance, but might be too tall or yield too poorly.
So the challenge is to incorporate the right mix of genes through natural selection that will result in a Sclerotinia-tolerant parent line that also has sufficient agronomic and end-use qualities, as well as genetic resistance to other diseases and potential problems. And once the right genetic package is obtained, Miller’s research group cannot release germplasm for commercialization unless performance is reliable, and that takes multiple years of testing in multiple growing environments.
Crosses increasingly complex
Pat Duhigg, Seeds 2000 of Breckenridge, Minn., began his sunflower breeding career in the 1980’s. Life as a sunflower breeder seemed simpler back then, with focus primarily on yield and oil content. He recalls flare-ups with downy mildew in the early ‘80s, but around 1985, Apron was approved for use with sunflower, and that took care of the problem.
But the 1990’s brought a new era to sunflower hybrid R&D. There was the outbreak of Sclerotinia. There were indications that strains of downy mildew were becoming genetically resistant to Apron. NuSun was developed. Research on Clearfield got underway. Niche markets sprang up for bird food, de-hull, and other uses.
“You can see how breeding programs have become a lot more complicated these days,” he says. “If you have a new trait, say for head rot resistance, it has to be incorporated into your linoleic hybrids for international markets, NuSuns, high oleics, imi-resistant hybrids, and down the line the SU (Sulfonylurea – Express) resistant hybrids.”
Duhigg laughs as he recalls a report to his sales people that one of his new hybrids included three different genes for disease and herbicide resistance, all through conventional breeding. The response from the sales group was “but can it be used as a huller?” Another breeder several years ago reported that she had to throw out a super looking experimental because it was two inches taller than a popular competitor hybrid. Her farmer cooperators simply said “it won’t sell because it is too tall.”
Indeed, it ain’t easy being a sunflower breeder.
Survival of the fittest
Challenges are even greater for confection sunflower breeding, says Jim Gerdes, sunflower breeder with Mycogen Seeds. It’s a smaller market with less resources dedicated to breeding, and limited public germplasm, particularly for large-seeded material, highly coveted in the confection market.
Demand for larger seed size is a key trend in the confection market, as is a shift from dual-purpose hybrids to hybrids specifically for in-shell or dehull. Gerdes says another trait that’s receiving greater emphasis is breeding larger kernels within the seed, for better marketability with consumers as well as growers – a larger kernel will bust out of the hull better after planting, resulting in better emergence.
But since multiple genes are involved with seed size and seed color, carrying these genes over to a confection hybrid is incredibly complex. Furthermore, it’s difficult to incorporate traits from oilseed germplasm, wild sunflower species, or from exotic germplasm from other sources of the world while maintaining seed size and color. So it becomes a numbers game, going through large populations of plants to find the right mix of desired traits.
In plant breeding, original plants being crossed are the parental (P) generation. Offspring from the parental generation are referred to as the first filial (F1) generation, and offspring of F1 plants are referred to as F2.
Sunflower breeder Jim Gerdes says that out of every 20,000 F2 sunflower plants in the Mycogen Seeds confection sunflower research program, about 500 are advanced to F3 – only 2.5% of the plants make the cut. The F3s are evaluated for seed size, seed color, seed set, self-compatibility, and general agronomics. Of these 500 plants, only about 50 (around 1% or less) will make it to yield evaluation.
“Out of your initial 20,000 plants, there’s a good chance nothing will make it to commercialization,” says Gerdes. “Imagine producing 20,000 prototypes, with the realization that nothing could make it to market.”
No, it ain’t easy being a sunflower breeder. There are lofty expectations. And the thing of it is, more often than not, sooner or later, sunflower breeders come through with products desired in the marketplace. Amazing when you think about it: herbicide and disease resistance, standability, seed size, yield and oil content all begin with that bag of seed.
The increased complexity of sunflower breeding these days is offset somewhat by marker-assisted selection, a research tool available today that was not 20 years ago. This genetic mapping technology is employed at the basic research level, primarily by molecular sunflower geneticists Jinguo Hu and Chao-Chien Jan at the USDA-ARS lab in Fargo, and several hybrid seed companies.
Their molecular research should not be construed as biotechnology – they are not taking the genes of one organism and inserting them into another. Rather, they are using molecular markers to identify where a particular trait is located within a sunflower plant's genetic makeup. The researchers map genes to point the way toward particular agronomic or quality traits within sunflower plants that may be desirable or undesirable in a commercially grown hybrid – it’s like marking a trail to navigate through the woods.
Once a gene has been marked, researchers can test for its presence in subsequent sunflower lines. The use of molecular markers on parent line germplasm allows breeders to bypass the need for screening hundreds of plants for the absence or inclusion of a desired or undesired gene, thus reducing backcrossing steps and bringing greater efficiency (and less expense) to the process of developing improved sunflower hybrids.
Obviously breeding is paying off in yield with reports of 3,000 lb yields on dryland fields common in 2005. Not many years ago, the yield bar was a ton, and now the bar has been raised substantially. The first NuSun hybrids were noted to have a yield and oil drag. Now in fourth and later NuSun generations, there is no longer talk of yield drag but yield enhancement. And without having to work so much on stabilizing oleic levels, breeders can zero in on improving aspects of disease resistance and yield, and these results are now showing up in the field. – Tracy Sayler, Larry Kleingartner
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