Estimates of genetic variances in two Spanish populations of maize

Reports of estimates of components of genetic variance in open pollinated populations of maize (Zea mays L.) have been mostly on U.S. Corn Belt germplasm, whereas few studies have been conducted using European germplasm. This study was undertaken to obtain estimates of genetic parameters for important agronomic traits in two populations (Ribadumia and Tuy) from northwestern Spain. Full-sib within half-sib groups were developed by the Design I mating system and evaluated at two locations in Spain in 1987 and 1988. The populations showed a similar genetic structure with very small differences. Moreover, the pattern of genetic variability was similar to other germplasm because the greatest proportion of total genetic variance was attributed to additive effects for most traits. In contrast, estimates of dominance variance were large for yield, ear, and plant height and ear length. In general, additive x environment interaction variances were significant while dominance x environment interaction variances were not significant for either population. The large range of variation and the high values of heritability for lodging and ear and kernels traits, as well as values of expected gain from selection for these traits, suggested good potential for improvement through an intrapopulation selection program. However, the large dominance effects and the small additive effects for grain yield indicated that an interpopulation selection program would be effective if the large intrapopulation dominance variance is expressed in population crosses. Yield did not show significant additive variance so estimates of additive correlation with any trait were not calculated. Correlated response between yield and any trait is not expected and improved grain yield based on indirect selection of yield components is not recommended.