GENESYS: a model of the influence of cropping system on gene escape from herbicide tolerant rapeseed crops to rape volunteers - II. Genetic exchanges among volunteer and cropped populations in a small region

The aim of the model GENESYS is to rank cropping systems according to their risk of gene escape from genetically modified. herbicide tolerant winter oilseed rape cultivars to rapeseed volunteers. The model integrates the effects of crop succession and crop management at the level of a region. The first part of the model presented by Colbach et al. [Colbach, N., Clermont-Dauphin, C., Meynard, J.M., 2001. GENESYS: a model of the influence of cropping system on gene escape from herbicide tolerant rapeseed crops to rape volunteers. I. Temporal evolution of a population of rapeseed volunteers in a field. Agric. Ecosyst. Environ.. in press], describes the temporal evolution of rapeseed volunteers in a field. In this paper, the temporal sub-model was extended to include the evolution of genotype proportions with time and the effect of genotype on herbicide efficacy, on seed and pollen production. The spatial dimension was introduced by modelling demographic and genetic evolution of rapeseed volunteers in all the plots of a region, whether they are cropped fields or uncultivated field margins and waysides. Each year, pollen and seed are exchanged between plots and the importance of these exchanges depends on plot areas and distances. and, in the case of pollen, on flowering dates. (C) 2001 Elsevier Science B.V. All rights reserved.