Of course there is a lot of rabid argument on both sides, however whilst it is now quite practical to identify how some certain genes modify the phenotype, it is not a perfect science yet. As a geneticist I'm sure you're aware of how whilst a particular gene may have a particular, obvious effect on one aspect of the phenotype it may have countless unseen side effects especially if it is reliant on other genes within the chromosome or the mutation is applied in combination with other changes. (So I gather from my brief education in genetics this term anyway.)

This of course is all fine in the lab where things can be controlled and confined but the main stem of the concerns comes from trials in the open where there is, despite sterilisation & the use of terminator technology, a small possibility of cross-breeding with other nearby crops. Whilst most people are afraid of Tryffids roaming the countryside, the problems are much more subtle than that and something only needs to go wrong once for a huge area to be affected. Of particular concern are the effects of herbicide & insect tolerance, should the crop interbreed with weeds or indeed become uncontrollable itself.

Also I'm not sure what the Soil Association rules are but I'm pretty sure that'd lose Farmer X a lot of money when he can't get that lovely "organic" stamp on his crop.

Of course Monsanto and Syngenta have been rolling out their crops in more relaxed areas, particularly across the pond, for years and haven't encountered any problems (with their seed at least).

Whilst I am not in any way anti-GM, I am very concerned that effective controls and contingencies should be in place, no matter how small the chances.

P.S. For a tongue-in-cheek article on "what hell science hath wrought lately", click here