GeneSys-Colza: a model for the medium-term and long-term effects of cultivation systems on the flows of genes between colza fields and new growth in a given agricultural area

The aim of the model is to evaluate the influence of cropping systems on tr ansgene escape from rapeseed crops to rapeseed volunteers in time and space . The model input variables are the regional field pattern, crop succession and cultivation techniques. The main output variables are, for each year a nd plot, the number of individuals per m(2) and the genotype proportions of the adult rapeseed plants, the newly produced seeds and the seedbank. The model comprises an annual life-cycle for volunteer and cropped rapeseed pla nts simulated for each plot and year; the relationships between the various life-stages depend on crop type and management. Pollen and grain exchanges between plots depend on distance between plots and cropping system. With t he help of the simulations performed with the model, it is possible to iden tify low-gene-flow cropping systems or the minimum distance between rape pl ots to avoid contamination of the harvest product, to estimate the conseque nces if one farmer does not manage his rope volunteers correctly etc.