1.   Scientists have known that genetically altered traits like resistance to herbicides can be transferred from crops to related weeds through cross-pollination.

2.   The gene exchange need not be a problem if closely related weeds are not in the area of the crops, Fehr said.

3.   The oilseed rape was planted in the field with a closely related weed, Brassica campestris, and hybrids resulted that looked like the weed.

4.   Scientists tracked the spread of natural genetic material from chloroplasts in oilseed rape to a related weed.