Engineered Plants Pass New Genes to Weeds, Study Finds

In an unsettling turnabout of modern farming’s biological warfare against weeds, a team of Danish researchers reported today that some genetically engineered plants designed to withstand herbicides can pass those new genes to nearby weeds, which in turn become resistant to chemicals meant to eradicate them.

Experts said the finding, reported in the journal Nature, is the first confirmation of what many critics of the new biotechnology have long suspected--that new traits introduced into genetically engineered crops in some instances can be inherited by nearby weeds and other wild plants that belong to the same general family.

University of California biotechnology experts said the new finding highlights the importance of meticulous review of each new genetically engineered plant variety and the genes involved in creating it. Altered crops must be closely monitored even after they achieve wide commercial acceptance, with special attention paid to the geographic regions where they are planted, they said.

“This is an important piece of work that confirms the very real risks of genetically engineered crops,” said Jane Rissler, a biotechnology expert at the Union of Concerned Scientists, a nonprofit lobbying group that addresses a variety of scientific issues. “This is a problem that could have serious consequences all around the world, depending on the crop, the location of its wild relatives, and the gene involved.”

The plant geneticists at the Riso National Laboratory in Roskilde, Denmark, did their experiments with a commercial crop called oilseed rape, which is raised widely in Canada and Europe to produce canola oil, and a closely related weed called Brassica campestris. Both plants belong to the mustard family.

The researchers found that the two plant varieties spontaneously cross-fertilized each other and, within a few generations, the resulting crossbreeds not only contained the new gene, but also were capable of passing on the new trait to subsequent generations.

“The occurrence of fertile, transgenic weedlike plants after just two generations of hybridization and back-crossing suggests a possible rapid spread of genes from oilseed rape to the weedy relative B. campestris,” they wrote. “And this should be taken into account when considering the consequences of transferring new traits to oilseed rape.”

U.S. farmers this year are expected to grow genetically modified plants in record numbers as new seeds created by biotechnology companies reach the market. Among the new crops are sugar beets and soybeans designed to tolerate high doses of weed-killing chemicals, as well as insect-resistant varieties of maize, potatoes and cotton, which reduce the need for chemical pesticides. The U.S. Department of Agriculture has in recent years approved hundreds of experiments involving field tests of genetically engineered plants.

Commercial plant breeders covet the trait for herbicide resistance because it can allow farmers to use stronger doses of herbicide on weeds that have become naturally resistant to the chemicals without also killing crops. It also can allow them to use powerful herbicides that degrade faster and do not pollute the water and soil.

Monsanto Co., a leader in agricultural bioengineering, has developed a variety of herbicide-resistant canola, which it is testing in Europe. The resistant weeds that have evolved spontaneously as a consequence of its field experiments are “not very fertile,” a company spokeswoman said.

Plant Genetic Systems of Belgium also is marketing its brand of herbicide-resistant oilseed rape in Europe. Company officials could not be reached for comment Wednesday.

Several U.S. biotechnology experts said the recent finding in Denmark was no reason for a blanket condemnation of the products from biotechnology’s new horn of plenty.

“We think it has to be judged on a case-by-case basis,” said Calvin Qualset, director of the University of California’s genetic resource conservation program. “Each gene that is being introduced into a crop has to be judged on what it does to the plant and what it does to the environment in which it is grown.”

Calgene Inc. in Davis, for example, has created a genetically engineered commercial variety of oilseed rape, but it is not creating plants with herbicide resistance. The Calgene plants instead have been genetically altered to produce lauric oil, a saturated fatty acid and key raw material used in the manufacture of soaps, nondairy coffee whiteners, whipped toppings and other items. The plants have been field tested extensively in the United States.

Even if that new gene for lauric oil is incorporated into new varieties of weeds, it is not likely to be harmful in any way.