Farm Journal: Pollen In The Air
-From the pages of the May/June 2001 edition of Farm Journal magazine.
Imagine it's late July in the U.S. Corn Belt. Somewhere, a 100-acre field of corn is pollinating, casting to the winds some 13 trillion pollen grains. To that vision add that farmers will plant some 18.4 million acres of genetically modified (GM) hybrids this year. Add in the tens of thousands of acres of such things as GM inbreds, parent lines and experimental plots. Welcome to the land of milk and "adventitious presence." That's the latest buzzword for what happens when pollen ends up where it's not supposed to be. It was called outcrossing by seed companies back when their biggest concern was farmer complaints that a field was not consistent in plant height or color.
In the seed.
At a recent seed industry workshop on adventitious presence, Tom O'Connor, head of technical services for the National Grain and Feed Association, called for labeling seed corn bags with the amount of GM or other adventitious contamination present. "If you're buying an unapproved [trait], you should know that if you plan to market corn in an area where that event can't be sold," O'Connor says.
Seed companies fear labeling bags could be misleading and, until tolerances and testing standards are set, meaningless.
"The seed industry has always been concerned with outcrossing," says Tim Gutormson, president of Mid-West Seed Services, Inc. His company tests seeds for companies and foundation seed developers, looking for everything from simple germination information to genetically modified content.
In the past two years, Gutormson's company has seen increased demand for genetic purity testing. "Now that we've gone through the Cry9c [StarLink] situation, it's definitely raised the bar in the amount of genetic purity testing seed companies are doing," he says.
That should be good for farmers, he says. For example, federal law stipulates that a bag of seed corn be 95% hybrid seed. While most companies strive for only 1% or 2% impurity, or outcrossing of a hybrid, the StarLink situation has everyone learning just how good a job they were doing, and what areas to improve to meet zero tolerances.
"Historically, there has been a fair amount of work on pollination and pollen travel," says Mike Lauer, a research coordinator at Pioneer Hi-Bred International. "But there are a lot of things about it that we may never fully understand."
Tracking the wind.
Most seed production fields have 8 to 16 all-male border rows--an attempt to minimize outcrossing from a nearby field by overloading field edges with "correct" pollen.
For the adventitious presence study, researchers started at the innermost border row and sampled grain produced at intervals of 6.8', 31', 68', 118' and 660' into the field. The percentage of outcrossed seed was averaged over all fields.
Wind conditions year to year were critical, Lauer reports. "How one year's wind patterns varied from another's, and the influence on pollen movement, is tremendous."
In 1998, average adventitious contamination was 0.9%. In 1999, contamination was 1.7%. Data from 2000 hasn't been fully examined.
"Increasing the distance [from other corn] tends to decrease outcrossing," Lauer says. As predicted, samples from far inside the field had lower amounts of contamination than did rows near the outside.
But the drop in contamination across any field was not linear, with hot and cool spots at various distances. Those peaks and valleys of contamination varied greatly from field to field.
"One thing we don't fully understand is how much influence wind turbulence above the field has on mixing pollen from that field and nearby fields," Lauer says. "You may think a wind break would be a good thing, slowing wind and decreasing how far pollen goes. That may not be true."
Pollen worries don't stop with crops that cross-pollinate. "The cotton seed market in Greece, a premium-priced market, isn't driven by science," says Chip Sundstrom, executive director of Parsons Seed Certification Center at the University of California, Davis.
To keep the high-value Greek market, California seed producers must guarantee zero GM content.
Cotton, like soybeans, is a self-pollinating crop. Yet Roundup Ready and BXN cotton are popular in the same areas where premium cotton seed is produced. "We've learned that cotton pollen is the top source of honey in California," Sundstrom says.
Role of bees.
"We found outcrossing from 0.2% up to 1%," Sundstrom says. "We found cases where outcrossing was 0.1% up to a mile from other cotton. And these are fields that get a lot of insecticides. I was out in those fields and there were basically no bees, no insects of any kind."
The center will conduct more rounds of pollen tests this year to get a better feel for common flow levels. Sundstrom also plans to test nearby bee hives to see how much GM pollen bees may be carrying and if they are actually the culprits.
What seed production changes seed companies may have to make also depends on what tolerance levels are allowed.
"StarLink taught us that zero tolerance won't work," says Gutormson. "Before companies can really say they're doing an adequate job of isolation, we have to know what tolerances they have to meet."
Seed companies prefer more standardized tolerances for new traits. "It's going to be very difficult to establish a threshold for all unapproved varieties," says Michael Schechtman, USDA's biotechnology coordinator. "You can't pass judgment on the safety of [modified] organisms that have not even been evaluated yet."