The understanding of gene-environment interaction is a crucial issue in plant breeding.For this objective,mechanistic models of plant growth can help disentanglethe genotypic and environmental effects.Each genotype is characterizedby a specific vector of model parameters and ideally,these parameters arestable for a certain range of environments.As explained in [2],each parametercan be seen as resulting from the influences of several genes (epistasis),while the same gene can influence several parameters (pleiotropy).