Corn's casual attitude toward sex is great for making hybrids. Corn flowers willingly accept pollen from any maize source. That's a problem, however, when genetic purity is an issue.
It's an issue that has Iowa State University Agronomist Mark Westgate and others tracking down how pollen travels and how to keep it at home. “Genetic purity becomes an issue when you start dealing with transgenic vs. non-transgenic hybrids, organic crops and pharmaceutical crops,” Westgate says. “The future of agriculture is moving toward traits grown in specialty crops. The volume of crop produced won't be as important as what is inside the seeds.”
Traditionally, there's been an understanding in the industry that there are economical and practical limits to genetic purity in hybrids. And, that wasn't an issue until specialty crops, like corn grown for pharmaceuticals, entered the market. “We don't want those proteins in the food chain,” Westgate says.
Westgate joined with other scientists to study the biology of the corn flower and how atmospheric conditions affect its travel. “We wanted to gather ground truth information on how pollen is produced and how it travels in the atmosphere,” he says. “The goal is to develop a computer model that accurately predicts pollen movement.”
THE USDA ANIMAL and Plant Health Inspection Service (APHIS) has set isolation standards for growing pharmaceutical crops. Westgate established test plots using APHIS isolation criteria on farms operated by Joe and Bill Horan near Rockwell City, IA. Westgate planted a small plot of purple corn in the middle of a section of soybeans. Pollen traps set across the field captured windborne pollen and a receiver corn crop planted around the field perimeter demonstrated if any pollen reached that point.
“We've found that the biology of the corn flower is very predictable. Pollen density increases exponentially with distance. About 99% of the pollen falls within 100 ft. of the plant that produced it,” Westgate says.
But, some of that remaining 1% traveled as far as the edge of the field — ½ mile from the source crop. “We might find two purple kernels on an ear with 500 kernels,” he says.
In further study, Westgate planted a sorghum crop around the central plot to see if that would reduce pollen drift. “We created a biological wind barrier approximately 5 ft. taller than the purple corn crop. We found that we could reduce wind speed by 2 mph. That doesn't sound like a lot, but it significantly reduced pollen drift,” Westgate says. “We're continuing the study to try and determine what kind of biological barrier design works best.”
WHILE COMPUTER MODELS created by Westgate and the other researchers he's working with will predict pollen travel, it will never be possible to prove zero contamination from pollen drift.
“We can help make sure it doesn't happen, but we can't prove it didn't happen,” Westgate says.
It's an industry dilemma. “It would be a very positive message if the government would encourage the industry to accept some level of impurity, just as it does with other food products,” Westgate says. “If that doesn't happen, the costs of getting transgenic crops and livestock to the market may prove prohibitive. The industry interest in some of these products is drying up.”
In the meantime, Westgate and others will continue their research, looking for ways to keep pollen in its proper place.