what happens to a gene deferred?


In this experiment at CIMMYT, the international corn and wheat research center, genetically engineered herbicide resistance failed. Note the dead zone where herbicide was painted on the leaf. Photos © David Tenenbaum
  Is it smart to teach plants to resist herbicides?
While insect resistance could reduce the amount of chemicals used on crops, herbicide resistance could increase it. Nonetheless, several seed companies have already made transgenic crops with immunity to herbicides that would normally kill them. This allows farmers to spray the field with herbicides after the crop emerges from the ground, zapping the weeds.

wheatOn the face of it, the idea seems unlikely to be adopted on environmental grounds. Yet if the chosen herbicide is less toxic than the one presently used, it could have benefits. And certainly, Roundup, generically called glyphosate, the herbicide to which Monsanto has conferred resistance in soybeans and other crops, is less toxic than most herbicides. Glyphosate stays where it's put in the field and breaks down quickly.

But problems can arise. In 1997, thousands of acres of supposedly Roundup-resistant cotton were killed in Mississippi by the herbicide. Monsanto says it has reached settlements with two dozen farmers (see "Cotton Growers Say Strain Cuts Yields" in the bibliography). "We concluded it was a combination of unusual weather patterns and generous use of Roundup," says public relations director Karen Marshall. "We'll give better directions next time."

Furthermore, glyphosate drift could affect plants outside fields. And the advent of Roundup-resistant poplar trees has raised the specter of vast tracts of diverse northern forests being converted to huge monocultures.

Ruining the relatives
To some extent, plants can transfer pollen -- and genes -- to related plants. That creates the potential for transferring inserted genes from the crop to other plants. Could weeds gain resistance to Roundup? The idea got a boost when Norman Ellstrand, a professor of genetics at the University of California, Riverside, showed that weeds hybridized with radish plants in 1994. "Hybridization between crops and weeds can lead to avenues by which undesirable traits can enter wild populations," Ellstrand said at the time. The problem traits could include herbicide and insect resistance, and tolerance to cold, drought or salinity.

Suketoshi Taba, a breeder CIMMYT in Mexico, examines a new hybrid corn made with conventional breeding. If they crossbreed with crop relatives, hybrid and transgenic corn could harm essential sources of new genes.   hybrid Perhaps more important is the related question of whether the new genes could pollute a crop's relatives. Should transgenic corn be grown in the regions of Mexico where corn originated, where wild relatives and old corn varieties both provide genes for insect or disease resistance to new varieties of corn?


  That idea gives corn breeders the shivers, since it could harm the source of genetic diversity that underlies all conventional plant breeding. And yet Monsanto's Karen Marshall says it could be done, with an adequate plan for preventing gene transfer. "It's a management problem. We would still sell the seeds there."

Allergic reactions
We've already learned that genetic engineering of crops can backfire. For example, a effort to insert a protein-producing gene from a Brazil nut into soybeans was short-circuited when people who were allergic to the nuts showed an allergic reaction to the beans in skin and blood tests (see "Genetic Engineering of Crops Can Spread Allergies" in the bibliography). Pioneer Hi-Bred International, the seed company which had sponsored the tests as a way to create a high-protein soy feed for animals, "decided not to proceed with further development of this product since there was no easy way to completely exclude these soybeans from human food processing and distribution system," according to Rod Townsend, the company's director of regulatory affairs. He notes that the soybeans never entered production, and never entered the human food chain.

Yet as more genes are transferred across more species lines, without any requirement for warning labels, such problems could become more common. An estimated two percent of adults and eight percent of children have food allergies, which can be deadly.

Organic standards
The U.S. Department of Agriculture has proposed a rule to allow genetically-engineered crops, along with irradiated food (see The Why Files coverage), to be labeled "organic." That rankles advocates of organic farming, who say the term should be defined to protect against such artificial growing and preserving technologies and not include them.

Taking the long view
So do genetically-engineered crops make sense? Farmers and seed companies surely think so, judging by their rapid introduction and acceptance. And even the skeptics, aware that feeding the world's billions is not going to get easier as the population surges, urge caution rather than outright cessation.

"When you go to release organisms into the environment, you're never 100 percent sure what's going to happen," says David Pimentel, who studies the environmental impact of agriculture and other resource-consuming activities at Cornell University (see "Genetic Engineering in Agriculture and the Environment" in the bibliography). He notes that at least 128 crop plants have started acting like weeds, proving that the law of unintended consequences is alive in agriculture.

Genetic engineering, he says, "is not inherently good or bad. I think you have to be cautious. We get more than 99 percent of our food from the land."

Want to surf our transgenic resources?


nothing
The Why Files
back story map More!

NISE/NSF


nothingThere are 1 2 3 4 5 6 pages in this document.
Bibliography | Credits | Search