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Pollen tracker

Bob Dylan's “Blowin' in the Wind” was a huge hit for folk singers Peter, Paul and Mary in the 1960s. Forty years later, that refrain has an altogether different meaning for corn production.

Using a computer-based software program, researchers at Iowa State University (ISU) are combining hybrid information, field design and local weather conditions, especially wind, to predict the genetic purity of hybrid seed corn. The computer-based program enables researchers to determine how much pollen is produced by a field of corn, when it is produced, where it goes and what happens to it when it's distributed to a neighboring field, explains Mark Westgate, an ISU crop physiologist. His work focuses on corn and soybean reproduction.

Knowing the level of genetic purity within a field of corn long before harvest will give farmers time, and therefore flexibility, in determining how to market their crops.

“Say your contract is for GMO [genetically modified organism]-free seed, and you find there was considerable risk of out-crossing during pollination. Then you have time to decide where to sell that crop, perhaps for animal feed,” Westgate says. “Keeping hybrids pure is increasingly a challenge. The model helps us assess the risk of pollination in a field of corn from foreign pollen.”

Not ready for growers

Westgate says no decision has been made at this point on how to market the PC-based software program to the corn industry. He says the investment to corn growers could range between no cost, if the program were made available via the Internet, to as much as $500, a price typical these days for a software package.

Westgate says that although the computer-based model is not ready for commercial use, it is working effectively in university research projects. “We are ground-truthing the model now across various corn production management practices and field conditions to ensure it stands up to real-life conditions,” he says. He adds that through the use of the model, this is the first time corn researchers have been able to couple the biology of plant flowering with the physics of pollen movement.

Preventing out-crossing

Historically, corn growers and seed companies have employed isolation methods to prevent out-crossing by foreign pollen in their corn crops and hybrid seed production fields. With the increased use of GMOs, however, the need to prevent out-crossing has increased.

“We do need to better understand how pollen moves,” says David Dornbos, global head of production research for Syngenta. “Purity standards are becoming more stringent, and we want to ensure that farmers get the quality of seed they need and expect.”

Dornbos says the ISU corn pollen dispersal program offers seed companies several potential benefits. It can help companies make more informed decisions about the spatial isolation requirements of cornfields for seed production as well as how effective the use of male border rows are in preventing out-crossing. He says the same factors that benefit seed companies will, in turn, benefit corn growers. “It's simply a function of scale,” he says. “The same theories and information should apply to farmers.”

Westgate agrees. He says the program will help farmers determine how to manage specific hybrids and specific fields more effectively during the next growing season. “By knowing my risks, I can better determine whether I might need more border rows or a windbreak on one side of the field to keep that particular corn hybrid pure,” he says.

GMO-free crops

The issue of genetic purity was underscored during the American Seed Trade Association (ASTA) annual meeting this past December. During that event, Joe Burris, a consultant to U.S.-based seed companies, shared highlights from a two-year, interindustry study he conducted on their behalf. He says the study was conducted to help companies establish their risk level for out-crosses in seed production fields and determine how to improve current purity standards.

Burris has developed a brochure for growers that outlines guidelines for producing non-GM corn and soybeans. The guidelines address factors such as field and seed selection, isolation strategies, harvest and storage needs, and record keeping. To receive the brochure, e-mail Burris at or call him at 515/232-8290. Additional information about genetic purity and GMOs, in general, also is available under “new technologies” at ASTA's Web site,

Pollen production

Westgate says that in addition to helping researchers determine genetic purity, the pollen dispersal program also helps them better understand pollen production and the role it plays in kernel formation and yield.

“When farmers planted for 24,000 to 26,000 plants/acre, those lower populations allowed the hybrids more room to capture sunlight and moisture and improved their ability to withstand poor environmental conditions,” Westgate says. With the higher populations and under certain production schemes, hybrids find it difficult to pollinate adequately for good kernel development and ear fill. If pollen shed and silk emergence fail to coincide or overlap well, called asynchrony, then inadequate pollination results. Westgate says when farmers push plant populations to 30,000 or more plants/acre, pollen shed does not always cover the late-emerging silks. The result: Ear tips don't fill completely, and targeted yields can be missed.

Westgate explains that because hybrid development in the last 20 years has focused on ear development instead of tassel development, modern corn hybrids are producing less pollen in general. Less pollen availability, along with poor environmental conditions and higher plant populations, increases the risk for less-than-stellar crop yields.

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