Genotype x environment interactions in maize hybrids from temperate or highland tropical origin

Exotic germplasm is often used in maize (Zea mays L.) breeding programs. However, the occurrence of genotype X environment interactions (GEIs) may mask the potential utility of exotic material. Our objective was to understand better GEIs for temperate, temperate X highland, and highland tropical maize genotypes cultivated under temperate or highland tropical conditions. We related yield instability to GEIs observed for vegetative or flowering traits, and determined the response of these vegetative or flowering traits to temperature and photoperiod. Forty-one hybrids grown in four environments were observed for several pre-flowering, flowering, and yield traits. Grain yield variation was related to two major adaptation factors: disease resistance and planting-to-silking duration (PSD). Yield variations were also related to variation in traits measured before flowering, such as emergence duration or early growth. For emergence duration, leaf stage at a given date, or leaf size, one simple temperature covariate accounted for more than half of the interaction sum of squares. Temperate X highland tropical hybrids had an intermediate behavior and were more stable than the pure temperate or pure highland tropical hybrids. For total number of leaves, photoperiod at tassel initiation explained a higher proportion of the interaction sum of squares than temperature. The response of highland tropical hybrids to photoperiod was larger than for the temperate hybrids. We recommend breeders who wish to introduce exotic material into adapted material utilize mass selection and/or advanced backcrossing, with marker assisted selection for specific traits with low heritability, such as cold tolerance.