I would like to pose some questions on two important areas for review.

1.Breeding systems and their implications for GM crops.

The relevant questions for answer include the following:

Do current genetic manipulation techniques affect, incidentally, crop breeding systems? For example, is outcrossing of cereals higher in GM crops? In small grains such as wheat and barley outcrossing is a low percentage; does genetic manipulation increase this as a side effect? Are the complex incompatibility systems in Brassicas altered in GM forms to the point that crossing barriers are removed or weakened?

These are basic questions in considering gene flow from GM to conventional cultivars. Current debate rarely mentions fundamental breeding biology which is of course of central importance.

2. How readily can gene flow occur from GM crops to wild species?

This is central to much of the debate. Crossing of the species barriers in the wild is normally very rare. Taking cereals, for example, we see no evidence of the establishment of genes from wheat or barley into wild species and this is general. Work we did some 20 years ago, and paralleled by more detailed studies by Bennett and colleagues at the old Plant Breeding Institute at Cambridge, showed that trans-species hybrids could be made for certain festucoid cereals but with difficulty, yielding hybrids of poor vigour and viability. Has the situation changed with GM cvs? Evidence for GM oilseed rape suggests that gene flow to wild relatives is very rare and that hybrids do not establish in the wild.

We are now often dealing with very unusual gene combinations not seen in the wild - for herbicide resistance for instance. Is there any evidence that pathogens such as Crown Gall, which was used as an early vector for gene transfer and which is widespread in soils and with a wide host range, are implicated in gene transfer from GM to widely-separated species?

I realise that answers to some or all of these questions, as well as to many others, may already be available. I strongly agree that the challenge is to help the public to understand what is known with some certainty and what is not. The scientific community faces a difficult challenge here and can only make headway with the support of informed politicians and an informed and sympathetic media.

Professor J E Dale