"Special genes inserted into crop plants have a way of leaking into the environment. That much scientists know for sure. What they're less certain about is what effect those genes have on plants growing in the wild.

Andrew Stephenson is interested in answering that question. He's a plant ecologist at Penn State University. Plant breeders put things called transgenes into plants to give them desirable properties such as disease resistance.

'People were concerned that when the transgene escapes into the wild populations, it will provide a fitness advantage,' says Stephenson.

A fitness advantage means the wild plants, with this advantageous transgene, might grow out of control, mucking up the ecosystem."

Joe Palca reports for NPR October 27, 2009. [2]