Genotype x Environment Interaction for Plant Density Response in Maize (Zea mays L.)

Increased adaptation to high plant density has been an important factor in improvements in grain yield in maize (Zea mays L.). Despite extensive public literature on variation and improvement in plant density response among maize varieties, much less public information is available on effects of environment and genotype x environment interactions (G x E) on plant density response for grain yield in maize. The present study was conducted to quantify environment effects and G x E effects on plant density response for maize grain yield. A set of 57 synthetic populations, synthetic x inbred line crosses, and synthetic x synthetic population crosses were evaluated across a five year period including 17 individual location-years. The data in this study were an unbalanced combination of multiple experiments that included 370 pedigree-environment combinations with each containing at least four planting densities and two replications per environment in most cases. G x E accounted for 26% of total genetic variance (genetic variance plus G x E variance) in linear regression coefficients and 39% of variance in quadratic regression coefficients in the regression of grain yield on observed plant density. Variance in G x E for linear and quadratic regression coefficients resulted in variation in optimal densities among varieties being highly specific to individual environments. Average plant density responses varied widely among environments with average optimal plant densities ranging from 5.6 to 9.1 plants m(-2).