Interpretation of Genotype × Environment Interactions for Early Maize Hybrids over 12 Years

Abstract

Genotype × environment interaction was investigated for grain yield of early maize (Zea mays L.) hybrids. Data were obtained from the French Association Générale des Producteurs de Maïs trial network and included 132 hybrids and 229 environments over 12 yr, following an unbalanced design. Analysis of genotype × environment interaction was done for the 1‐yr data sets, for the two successive years data sets, and for the 12‐yr data set. The magnitude of genotype × environment interaction variance was equal to, or greater than the genotypic variance. Interaction effect was modeled by factorial regression analysis using additional genotypic and environmental information. Genotypic covariates considered were the sum of growing day degrees (GDD) necessary from sowing to flowering and the GDD necessary from flowering to maturity. Environmental covariates were the mean temperature from sowing to the 12 leaf stage, the mean temperature from the 12 leaf stage to the end of the linear grain‐filling stage, the water balance around flowering, and the sum of solar radiation around flowering. These six covariates explained about 40% of the interaction effect in all analyses, with equal contribution of genotypic variates (20%) and environmental variates (20%). Flowering earliness of hybrids, water balance around flowering, and mean temperature from the 12 leaf stage to the end of the grain filling phase were determinants of genotype × environment interaction for grain yield in the considered area. A biological interpretation of the interaction was attempted through examination of the regression parameters.