Interpretation of genotype by environment interaction in two sunflower experimental networks

Genotype by environment interaction was investigated for sunflower grain yi eld in French official trials from two different networks. Genotype by envi ronment interaction was described using cross-product terms from factorial regression. This modelling provided parsimonious descriptions of interactio n: up to 20% of the sum of squares of interaction was explained using less than 7% of the degrees of freedom. It also made biological interpretation e asier. Genotypic earliness at flowering by environmental earliness, and gen otypic oil content by water deficit during the flowering period, appeared t o be two repeatable interactions: in both data sets, early genotypes perfor med better in early environments while late genotypes gave much better yiel ds in late environments, and the yield advantage of low-oil genotypes over high-oil genotypes was larger when water supply during flowering was non-li miting than in the case of water stress. Combined analysis of both data set s allowed us to compare patterns of interaction in both networks and to sel ect a more robust model.