Sir

Your News story “Transgenic crop trial's gene flow turns weeds into wimps” (Nature 421, 462; 2003) highlights the suggestion that gene flow between transgenic crops and potential weeds can act to lessen the latter's negative effects on important crop plants.

The researchers, Neal Stewart and colleagues, seem to reach this conclusion on the basis of short-term results consisting of a decreased negative effect of initial hybrid weeds on wheat yield when compared to the effects of non-hybrid weeds. Stewart et al. apparently attribute this to the reduction of fitness of other-wise well-adapted weeds through the inheritance of genes with high genetic load (that is, deleterious mutations) from the transgenic crop plant.

But the observation that initial hybrids are less aggressive and apparently unable to benefit immediately from such inheritance is not of much importance to agriculturalists. What is important is the evolutionary potential for transgenic crop genes to be shifted and shuffled around in a way that may eventually result in a novel modified gene complex.

Just as Clark Kent was able to change into Superman — as your News story put it — such a novel complex, initially born an inferior weakling, may very well have a chance of becoming a 'superweed'.