Gene in the
Although crops containing genetically modified organisms (GMOs) are considered “equivalent” to non-GMO crops by U.S. federal regulatory agencies, those selling to overseas and organic markets have found it necessary to segregate non-GMO crops and their food products from those containing GMOs. Commingling can occur at any stage during the food production process, but farmers are particularly worried that their non-GMO crops will be contaminated in the environment through cross-pollination with neighboring GMO crops.
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Isolation distances Corn is of concern because its pollen is transferred by wind. Up until now, maintaining the genetic purity of corn was primarily of concern to geneticists and plant breeders growing corn destined for producing certified seed for sale to farmers. Growing consumer resistance to GMO foods, however, has caused many farmers to examine ways of preventing GMO pollen from reaching their fields. The primary defense against unwanted crosspollination has been to establish buffer zones in the form of border rows or simply open distances between fields. In the United States, in most cases, these buffer distances are determined by official seed certification agencies for production of certified seed, not the federal government. Experts, however, don’t agree on how far pollen can travel. “Values are all over the map because pollen movement depends so much on weather conditions,” says Jerry Kermicle of the University of Wisconsin–Madison. Rather than rely solely on buffer zones to prevent cross-pollination, Kermicle believes that additional measures, such as genetic barriers that prevent cross-pollination (see sidebar on page 22A), are needed to ensure that nonGMO crops will remain GMO-free. © 2001 American Chemical Society
Transfer Environment Others in the industry have similar concerns because of how little is known about pollen movement. Although seed certification agencies require plant breeders and seed producers to plant seeds of one type a certain distance from seeds of another type, “isolation distances are based on data that was determined decades ago,” says Dennis Thompson, CEO of the Illinois Crop Improvement Association. “Corn is now being produced in geographical areas that were not included in that earlier data. We don’t know enough about pollen movement to predict what impact different weather patterns and conditions will have,” he says. A study by the Association of Official Seed Certifying Agencies (AOSCA) and several industry representatives is now under way in the United States to learn more about pollen movement. The study will include data, which should be available this winter, from more than 300 fields throughout the entire U.S. corn seed production area over three growing seasons, says Thompson. The results could shed some light on whether current measures to minimize crosspollination are effective.
Gap in federal authority Even with better data to support isolation distances, the three U.S. federal agencies that regulate agricultural biotechnology—EPA, U.S. Department of Agriculture (USDA), and U.S. Food and Drug Administration—have little legal authority to control contamination of non-GMO crops. “It’s more of a seed purity issue that is generally regulated by seed organizations, and in the case of exported certified seeds, by USDA,” says Chris Wozniak of EPA’s Office of Pesticide Programs. In other words, it is up to AOSCA to develop standards for the purity and identity of seeds grown in the United States. Whether these isolation distances and purity standards can be ap-
What can be done to prevent GMO crops from cross-pollinating with non-GMO crops?
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plied to the average farmer growing non-GMO grain remains to be seen. Under the Federal Plant Pest Act, USDA regulates GMO crops at the field-testing stage in terms of “importation, interstate movement, and release into the environment” (7 CFR, Part 340, 1997) in small, contained plots prior to commercialization. Researchers must obtain permission from USDA’s Animal and Plant Health Inspection Service and meet certain criteria and performance standards to grow GMO crops. For corn, there must be isolation distances of “660 ft or any greater distance that may be imposed by local seed certification rules” between transgenic corn plants that openly pollinate and any sexually receptive corn plant. After GMO crops have been field-tested and shown to be free from any risk under 7 CFR Part 340, they are typically deregulated by USDA through a petition process that was set up to promote the commercialization of field-tested transgenic crops. Once these crops are deregulated by USDA, growers are not under any restriction to isolate these cornfields from adjoining ones. Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), EPA’s purview only extends to GMO crops that have a pesticidal substance, such as the insecticidal endotoxin gene from Bacillus thuringiensus (Bt). EPA has no statutory authority over where traditional non-GMO corn varieties and organic corn are planted, says Wozniak. EPA does, however, require Bt-corn farmers to plant a certain percentage of non-Bt-corn. These so-called refuge requirements stem from attempts to manage insect resistance and have nothing to do directly with cross-pollination issues. The one exception is Aventis’s StarLink Bt-corn, the only GMO crop that was approved solely for animal feed and industrial uses. According to Wozniak, EPA required a 660-ft buffer, the standard distance set by
JANUARY 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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Gene barrier could prevent contamination of non-GMO corn Although experts agree that the likelihood drops off significantly as the distance from the transgenic corn increases, there is still a possibility that nonGMO corn will become contaminated via pollen from GMO corn growing in a nearby field. Rather than use isolation distances to physically separate crops in the fields, Jerry Kermicle of the University of Wisconsin Madison has found a unique way to prevent non-GMO corn from being contaminated by GMO corn. Working with teosinte, Kermicle discovered a block of genes that acts as a barrier against foreign genes, including those from GMO corn. Using conventional crossing techniques, the gene barrier can be bred into modern corn to prevent cross-fertilization with unwanted strains. “Corn was domesticated from teosinte. We are just going back to the mother plant and incorporating by conventional crossing something that got left out the first time,” says Kermicle. A certain amount of serendipity was involved in Kermicle’s discovery. “We were making crosses for another reason and found that we had great difficulty
hybridizing teosinte with corn,” explains Kermicle. That was in 1973, long before plants were genetically engineered via transgenesis, he says. Following that observation, Kermicle set out to study the genetic basis of the barrier. “Many plants have a mechanism to prevent fertilizing themselves. We call it self-incompatibility. That has been well studied genetically and molecularly. But I don’t know of a single case where people have studied the genetic basis of barriers that prevent wide hybridization in plants, which I call cross-incompatibility,” says Kermicle. Some in the industry are wary of the idea because it sounds too much like the controversial terminator gene, which renders seeds from GMO crops sterile. “Cross-incompatibility does not prevent plants from fertilizing themselves and reproducing their own kind,” says Kermicle. “It’s simply nature’s way of protecting the outer bounds of hybridization.” Others believe the barrier may be unnecessary because the risk of crosspollination is slim. As one expert put it, “Corn pollen is relatively heavy and
John Doebley
corn breeders to maintain genetic purity, surrounding StarLink corn because of crosspollination concerns. The non-GMO corn grown in the surrounding buffer zone must be harvested with the StarLink crop and segregated as a unit for animal feed and industrial uses (e.g., alcohol production). Aventis and EPA have agreed not to renew the registration of StarLink because of public concern, legal implications, and the huge economic losses incurred by farmers, food manufacturers, and Aventis itself, when StarLink made its way into the U.S. food supply last fall, spawning recalls of taco shells and other corn products. It is Teosinte (Zea unclear whether cross-pollination was m exicana),show n involved in the StarLink contamination. on the left,is believed to be the ancestorof In terms of cross-pollination, EPA is m odern-day corn. authorized under FIFRA to investigate the possibility of GMO crops crossing with wild relatives that are genetically compatible. “Fortunately with corn we don’t have much to be concerned about in the United States because there aren’t any wild relatives,” says Wozniak. Several species of teosinte, a wild grass that is believed to be the ancestor of modern day corn are, however, native to Mexico and Guatemala. There are concerns that genes from GMO corn could hybridize with teosinte, increasing its fitness and allowing it to proliferate as a weedy aggressive species. But most experts agree that, with the exception of some populations of wild
large, and it typically falls within 20 ft of the field. In most cases, the 660-ft standard distance is more than adequate.” A violent thunderstorm, however, could transfer pollen over greater distances, experts say. Still, critics argue that corn pollen is short-lived (less than 1 hr), and just because the pollen is transferred doesn’t mean hybridization or gene transfer will occur. For the most part, however, experts in the industry agree that the gene barrier is good news. “Our methods of detection are sensitive enough that we can detect even trace amounts of GMOs that end up in crops through cross-pollination,” says Dwight Denham of Strategic Diagnostics, a manufacturer of immunoassay-based test kits for detecting GMOs in food products. Because the economic stakes of GMO contamination are so high for traditional non-GMO growers targeting certain foreign markets and organic farmers, “anything that can prevent conventional corn from being affected by a transgenic event is a good thing,” he says. B.E.
cotton in Hawaii and Florida, cross-pollination of EPA-registered GMO crops with wild relatives is of no concern in the United States. Still, some advocates warn that even though teosinte does not grow wildly in the United States, environmental responsibility goes beyond national borders. “Bt-corn is in Mexico, whether legal or not,” one expert panel member reminded EPA at a meeting in October on issues surrounding the assessment of the risks and benefits of Bt-plant pesticides. The lack of legal federal authority to control the crossing of GMO crops with non-GMO crops points to a gap in the current three-tiered U.S. system for regulating agricultural biotechnology. At the same time that this gap exists, there also appears to be some degree of overlap among the agencies. For example, as Janet Carpenter of the National Center for Food and Agricultural Policy pointed out to EPA’s Science Advisory Panel at the October meeting, “For the Bt crops, both USDA and EPA assess environmental risks, such as gene flow and weediness.” Carpenter questioned whether this overlap is necessary and whether the standards are even the same. Many in the industry believe the United States would be better off with one agency instead of three regulating GMO crops. The U.S. Senate is even considering the option and recently formed a biotech caucus, co-chaired by Tim Hutchinson (R-AK) and Christopher Dodd (D-Conn.), to examine whether a single agency would be more effective. Britt E. Erickson is an associate editor of ES&T.
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