BIOTECHNOLOGY AND GENETIC DIVERSITY EXPERTS

SAY RISKS AND BENEFITS OF BIOTECHNOLOGY

MUST BE WEIGHED ON A CASE-BY-CASE BASIS

Could plant biotechnology affect wild ecosystems?

Critics fear a genetically enhanced gene could "escape" from a farmer's field and breed with a wild relative to create a "superweed" that could overwhelm the natural environment and curtail genetic diversity.

Proponents, on the other hand, say the productivity gains of genetically enhanced ' crops allow more food to grow on existing farmland, which preserves natural areas from being plowed under to feed a growing population. This, supporters say, promotes genetic diversity.

Researchers increasingly say the question is no longer whether a genetically enhanced gene, or transgene, will "escape." Pollen flow between plants is a natural phenomenon that has been occurring for thousands of years.

Indeed, a 1999 study found that 12 of the world's 13 most important food crops hybridized with at least one of their wild relatives. As Klaus Ammann, director of the botanical garden at the University of Bern in Switzerland puts it, "I can assure you that pollen did not learn to fly with the transgenes." So release of genetically enhanced genes is as likely to occur as with conventional varieties.

But the better question to be asked is what could happen when specific genetically enhanced genes do enter the natural environment, says John Burke, a biology professor at Vanderbilt University in Nashville, Tenn.

"Our work ... indicates a clear need to assess the relative risks and benefits of genetic modification on a case-by-case basis," he wrote in a paper titled, "Assessing the Risks of Transgene Escape: A Case Study in Sunflowers."

While there is much to study, most experts have concluded that the process of genetic engineering does not pose any unique risks to the environment.

"So far, most scientific inquiry into the subject has failed to support the notion that there is something about the genetic engineering process itself that intensifies any threats from gene flow," states an August 2003 report titled "Have Transgenes, Will Travel," issued by the Pew Initiative on Food and Biotechnology.

A panel of experts assembled by the National Academy of Sciences reached a similar conclusion.

"The genetic engineering process, per se, presents no new categories of risk" to the environment compared to conventional breeding, said the August 2002 report titled, "The Environmental Effects of Transgenic Plants."

Background

Although there is no question that the natural process of gene flow via pollination does occur, a number of conditions must be met:

First, there must be sexual compatibility between a domesticated crop and its wild relative for gene flow to occur – just as a bird cannot successfully mate with a frog.

Second, the plants need to be close enough so the pollen can move from plant to plant (pollen from canola, for example, can travel farther than pollen from corn).

Third, the plants need to flower at the same time.

In general, biotech crops that can easily hybridize with their wild relatives could theoretically pose greater risks than those that don't, explained Burke.

Because there are no wild relatives of corn or soybean in the United States, for example, researchers say there is no chance for genetically enhanced genes from either crop to breed with a wild relative. So the risk of any ecological problems from these crops in the United States is very low.

But there are wild relatives of corn in Mexico and wild relatives of soybean in Korea and China. So the same crops can potentially pose different risks of breeding with their wild relatives depending on where they are grown. That's why experts like Burke say genetically enhanced crops must be studied on a case-by-case basis.

Similarly, different genetically enhanced traits pose varying degrees of risk. A gene for herbicide tolerance, for example, isn't likely to confer an advantage to a plant in the wild because herbicides won't be encountered there.

But other traits – such as resistance to pests, disease or hostile growing conditions such as drought — could theoretically give a weedy relative an upper hand, says Burke.

Burke studied sunflowers (which have been developed but not approved for market) that have been genetically enhanced to resist white mold, one of the most widespread diseases that can cause yield losses of up to 70 percent. Because cultivated sunflowers are grown in regions where wild sunflowers are common, Burke says "crop-wild gene flow is a virtual certainty."

But what he concluded was that although the transgene for mold resistance was transferred to wild sunflowers, it "will have little effect on the evolutionary dynamics of wild sunflower populations." It appears that wild sunflowers already have resistance to white mold, so the additional white mold resistance gene didn't allow them to survive any better.