PERSPECTIVES Summer 2000: Assessing the Risks of Protecting Plants
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Assessing the Risks of Protecting Plants

Photo by Herman Lankford

he adoption by society of new technology or new ideas is sometimes fitful — a two-steps-forward, one-step-back shuffle. Thus it is with the powerful new discipline known as genomic science and the genetically modified organisms it makes possible.

The jury of public opinion seems still to be out on whether genetically modified organisms (GMOs), plants and animals that incorporate genetic traits designed to make farmers more productive, should play a role in agriculture. For a time, the public, at least in the United States, seemed unconcerned about genomic science and the vast potential it seems to offer for improving agricultural productivity. Lately, however, the pendulum may be swinging the other way. Particularly in Europe, there seems to be considerable concern about what are seen as risks from moving genetic material from one organism to another.

Yet wherever the pendulum of public opinion does come to rest, it would seem likely that a report completed recently for the National Academy of Sciences will play a significant role in the debate. The report, with the daunting title of Genetically Modified Pest-Protected Plants: Science and Regulation, benefitted significantly from input from the College of Agriculture and Life Sciences.

The 12-member committee assembled to prepare the report included two College faculty members, Dr. Fred Gould, William Neal Reynolds professor of entomology, and Dr. Ernest Hodgson, William Neal Reynolds professor of toxicology. Gould chaired one of two subcommittees that produced the report.

A year in the making, the report deals only with plants that have been modified genetically to protect them from pests. Genetic modification to enhance agronomic characteristics such as yield or genetic modification of animals are topics for other committees and other reports.

The report concludes there is no evidence that any foods produced from genetically modified plants are unsafe for human consumption. However, in order to ensure public trust in and acceptance of GMOs, the committee suggested that what Gould called “holes” in government regulation of GMOs be closed.

“Certain types of genetically modified plants have been exempt from Environmental Protection Agency regulation,” Gould explained. “The committee felt this loophole should be closed.

“Crops that are produced using genes from closely related plants are not now regulated by the EPA, whether the genes are transferred by conventional breeding techniques or by transgenic techniques. The committee said that while there is no reason to expect more risk from transgenic than from conventionally bred plants, transgenic plants with genes from related plants should be regulated because of the great diversity of transgenic plants that may be coming to market and because of public concern.”

Better regulation would include more thorough testing of transgenic plants to ensure they do not pose a danger to human health.

As a toxicologist, it was Hodgson’s role to help the committee assess the risks foods produced from transgenic plants might pose to human health.

Hodgson said transgenic plants are now tested to determine whether they cause allergic reactions or any of a range of other toxic effects; however, the committee did not consider these tests sufficiently rigorous.

Toxicity testing, for example, should be expanded. Hodgson pointed out that the toxicity of forage crops is often tested by feeding the crops to lab animals. Yet the plant being tested may not be an appropriate food for an animal such as a lab rat. Tests should be developed that allow the toxicity of a forage crop to be determined by feeding the crop to the type of animal — such as a cow, pig, chicken or turkey — that would actually eat it.

New tests should be developed, Hodgson added, that determine more accurately whether transgenic plants contain allergens. He said such tests can be developed relatively easily, given adequate time and funding.

Critics of genomic science have pointed out that with the ability the technology gives scientists to move genes between dissimilar organisms, there is a danger of unknowingly inserting genes that produce allergens into plants that would not normally produce an allergen. And in fact, this has happened. Genes from the Brazil nut were inserted into a transgenic soybean cultivar. People who were allergic to Brazil nuts were allergic to the transgenic soybeans. Work on the project stopped when scientists realized what had happened.

While Hodgson and Gould acknowledged that such risks exist in the creation of transgenic plants, they pointed out that conventional plant breeding carries similar risks. In fact, the risks may be greater.

Genomic science allows far more precision in the selection and movement of genes from one organism to another. When a hybrid is produced by crossing one plant with another using conventional breeding techniques, the breeder has little control over which genes end up in the hybrid.

That’s one reason the committee suggested that more research is needed to better understand the risks inherent in conventional plant breeding, particularly when the effort is aimed at protecting the plant from insects.

“When you breed a crop to be resistant to insects, a lot of the time you don’t know where the resistance comes from,” Gould explained. It may be that in conferring resistance on a hybrid, the breeder has also made it harmful to humans who eat it. Yet in the long history of conventional crop breeding, acutely toxic plants have rarely been produced and have never been available to the public through large commercial markets. However, conventionally bred crops have not been tested for lower level chronic impacts on health.

“When you put a compound into a plant that kills insects, there is a risk,” Gould added. The committee stopped short, however, of suggesting increased regulation of conventionally bred plants. The cost of such regulation, he pointed out, would “effectively eliminate public and small business plant breeding efforts.”

There are risks associated with genetic manipulation in two areas, Gould said. Food safety may be jeopardized, and the environment may be damaged. These risks apply whether the manipulation was accomplished using conventional plant breeding or genomic science techniques.

As genomic science evolves there will be more potential for problems, Gould said. Until now, transgenic techniques have been used primarily to move single genes from one organism to another. Yet the technology is rapidly approaching the point that entire genetic pathways may be moved. As the technology becomes more powerful, Gould said, it will be necessary to scrutinize the resulting transgenic plants more carefully.

Particularly where protecting plants from insects is the goal, environmental risk assessment is a balancing act, Gould said. For example, among the successes of genomic science are plants that contain what is known as Bt, a substance that is toxic to insects. Bt is produced naturally by microorganisms, and scientists have successfully moved the gene responsible for making the toxin from microbes to plants.

If plants contain the toxin, insects that attempt to feed on the plants will be killed or repelled. Yet critics have pointed out that the toxin can kill or damage beneficial as well as pest insects. This is where society must begin to balance the gain from genetic manipulation against the possible negative consequences.

“You’re trying to determine a strategy that does more good — damage to pests — than bad — damage to beneficial insects,” Gould said.

“With something like Bt, it seems as though the balance is clearly in the favor of damage to pests. Bt tends to be very specific. Some types of Bt will kill only caterpillars, not beetles. However, Bt is in the plant, so it’s in the environment for a long time.”

The balancing act becomes more complex as other variables are factored into the equation. For example, the Bt gene has been inserted into cotton to control boll worms and the tobacco budworm.

“We know there’s a significant reduction in pesticide use” with Bt cotton compared to cotton that has not been genetically modified, Gould said. “There seems to be an environmental advantage.”

That may not be the case with Bt corn. Bt protects corn from the European corn borer, yet only a small percentage of corn is sprayed with pesticides to control the European corn borer. The pesticide reduction resulting from the use of Bt corn is small. The environmental advantage, therefore, may be minimal.

Critics of genomic science have also pointed out the danger of genes moving from a crop to wild relatives of the crop, potentially producing super weeds. Gould said the risk of this actually happening would seem small. He pointed out that corn, cotton and potatoes have been genetically modified most often. Wild relatives of these crops do not occur naturally in the United States.

Sorghum, on the other hand, is a different story. Johnsongrass, a weed, is a wild relative of sorghum, so the movement of genes would be a possibility. Thus the need for careful, thoughtful regulation — regulation that will allow society to reap the benefits of genomic science while avoiding the pitfalls.

“If you regulate carefully,” Gould said, “the risks would seem to be minimal.”

 


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