Sunflower production in the Minnesota, North Dakota and South Dakota region of the country has its challenges, but its an option that many growers prefer. That preference has been spurred on by the seed companies that have developed seed and weed control combinations to meet the growers' needs-even though sunflower growers don't have the weed control choices of other crop production.

Sunflower production is one area where the Clearfield technology system has shown its value and is a mainstay.

The Clearfield technology has been available for a decade but in recent years, it has received low attention other than from large acre niche crop and cereal grain growers.

Biotechnology crop production has been in the spotlight. Clearfield technology is not biotechnology but does impart tolerance to imidazolinone (IMI) family herbicides to crops through conventional breeding.

Clearfield is a BASF trademarked technology. Working with North Dakota State University (NDSU) and U.S. Department of Agriculture plant breeders, Mycogen and a couple other seed companies aggressively collaborated to bring Clearfield sunflower hybrid seed to market. Clearfield sunflower hybrids now dominate the sunflower seed business.

"BASF is not in the seed business. We don't own big seed companies and aren't into that part of the business," Vince Ulstad, BASF technical service representative, recounted. "In the case of Mycogen, they are one of our partners with Clearfield technology, particularly with sunflower. They are one of our leading marketers of Clearfield sunflower; they have had good success with hybrids in the marketplace and done a good job of breeding the traits into their nursery stock."

"Within the sunflower market, we have a dominant share," said Bruce Due, customer agronomist for Mycogen Seeds, but he also noted that NDSU had approximately 22 Clearfield sunflower hybrids in their trial plots in 2008.

In general, experimental hybrids in development are not in the university trials shown to the public. "The university trials are intended for those products that a farmer can go out and buy for his operation for the coming year, but we have a load of experimental hybrids coming down the pipeline with Clearfield technology," Due said.

From Wild Plants to Commercial Seed
Clearfield sunflower seed herbicide resistance is the only one transferred from a wild plant population to commercial seed. "The original gene that confers the tolerance to the IMI herbicides was isolated out of a wild population of sunflower in Kansas," Ulstad explained. Just recently, BASF isolated a gene with herbicide tolerance from a cultivated population of sunflower (commercial seed variety), and that find is fueling anticipated seed advancements for better sunflower.

"The genetics for Clearfield came from a wild sunflower species; therefore, in order to get it into conventional hybrids without dragging along the unwanted genetics, it has taken a lot of backcrossing," Due explained. The current gene being used in the industry is quite time consuming for breeding to eliminate any negative traits and also to require the gene be present in a homozygous relationship on both the male and female parent of a hybrid cross.

The cultivated population gene will allow even more Clearfield sunflower advances, according to both Due and Ulstad. It will allow breeding the gene into sunflower hybrids without both parents having the gene present, only one will be necessary.

"Number one, it will speed up the breeding process so that breeders can put it into more potential commercial hybrids faster. Second, it is going to bring a much higher level of tolerance to the IMI herbicides, and third, it is going to have a lot less background with it, especially for breeding confection sunflower to give breeders much more control over color and seed size and things desirable from a consumer perspective," Ulstad said.

All the other Clearfield technology crop seeds were originally discovered from commercial germplasm. BASF has identified Clearfield spring wheat, winter wheat, canola, corn and rice that is marketed in the U.S. Clearfield technology lentils are grown in Canada and soon should be grown in the U.S., Ulstad noted.

A Role for Commercial Germplasm
Wheat is a good example of how commercial wheat germplasm was used to identify herbicide-resistant genes. Different germplasm wheat seed was seeded into field plots and sprayed with herbicide to see if any plants survived and at what level of injury they survived.

The history has been that once the gene has been identified, then crop breeding associations, universities and seed companies are given the right to crossbreed the gene into commercial germplasm. With sunflower, Ulstad is quick to give Jerry Miller, Ph.D., with the U.S. Department of Agriculture Northern Plains Crops Laboratory, credit for actually isolating the gene from wild sunflower and incorporating it into some of the standard USDA breeding material that was then made available to sunflower seed companies.

Mycogen jumped on the chance to work with the new gene transfer and breeding. "The current situation with all the hybrids on the market is that they are using public genes. There is no tech fee and there is no licensing, although we do need to have a hybrid certified by BASF as tolerant to Beyond herbicide," Due said.

The original development work with sunflower was done using Pursuit herbicide as the IMI product, but Beyond is the current product with a fit on most of the Clearfield grass crops. "Beyond provides a wider spectrum of control with both broadleaf and grass activity than other herbicides and is the herbicide specified for use with Clearfield sunflower production," Due said. The herbicide provides post-emergent weed control and soil activity for residual control.

Awareness of Cross-Resistance
Ulstad explained that the sulfonylurea (SU) and IMI families of herbicides have the same ALS inhibitor mode of action. "Even though they are structurally and chemically different families, the mode of action within the plant is the same. Generally, if any weed has developed resistance to an SU, then the probability of cross-resistance to an IMI is extremely high and vice versa," he said.

Kochia resistance that developed to SU herbicides also has made virtually all kochia resistant to IMI chemistries, too.

Clearfield and other commercial wheat is a good example of the crop injury situation. "You could spray an SU herbicide over Clearfield wheat and have quite a bit of injury to the crop, probably not killing the plant, but there would be quite a bit of crop response," Ulstad said. Spraying Beyond over the wheat would not measurably impact the wheat.

Due notes that in addition to the sunflower business, ag retailers and Mycogen have a varied seed business across much of the sunflower territory that he serves. Growers in the Red River Valley and surrounding area have many options for crops to grow. Ag retailers and seed suppliers serving the area have to be ready for meeting demand as it rolls out each spring and fall.

"There are about 15 different crops that farmers can grow in any given year depending on which one is the hot one to grow. It certainly isn't as easy for these growers as those growing corn and soybeans only," said Due. "A grower has a lot to evaluate for what he is going to grow to make the most profit from the farm. From year to year, it may not be the same crop. Acreages kind of yo-yo; they are not stable and that includes sunflower."