THE COST OF HERBICIDE RESISTANCE IN WHITE-CHICORY - ECOLOGICAL IMPLICATIONS FOR ITS COMMERCIAL RELEASE

Applications for the commercial release of herbicide-resistant crops, most of them transgenic, are likely to become more frequent in the com ing years, The ecological concerns raised by their large scale use cal l for risk-assessment studies. One of the major issues in such studies is the relative fitness of the resistant line compared to the suscept ible when no herbicide is applied since this will largely determine th e long-term fate of the resistance gene outside of the field. Here we report on a comparison of a sulfonylurea-resistant line of white-chico ry regenerated from a non-mutagenized cell culture with a supposedly i sogenic susceptible biotype. The plants were grown in experimental plo ts at a range of densities in a replacement series. The reproductive o utput of the plants decreased with increasing density but no significa nt difference was found between the two lines for any vegetative or re productive trait at any density. This suggests that no cost is associa ted with the mutation causing the resistance and that the resistance g ene would not be selected against if it escaped to populations of wild chicories.