Genotype x Environment Interactions of Mean Genetic Components for Days to Silking and Grain-Filling Period in Maize.

The mean genetic components estimates for quantitative traits, m + a (contribution of homozygous loci) and d (contribution of  heterozygous loci),  are strongly influenced by genotype x environment interactions (GE), especially in tropical conditions. The effect of the interaction is particularly significant on traits such as the number of days to flowering (NDF) and the number of days to reach maximum dry matter accumulation in the grains (NDMG). The objective of this study was to verify the GE effect on m + a and d estimates for NDF and NDMG. F₁ and F₂ generations of nine commercial maize hybrids from different companies were evaluated in Lavras, Brazil, with three sowing dates: October 2014, January 2015 and October 2015. A split-plot design was used in which the whole plots were the hybrids and the subplots were the two generations, with four replications. The NDF was considered to be the date when 50% the plants in the plot had visible silks.  The NDMG was considered to be the number of days from silking until the appearance of a black layer at the base of the seeds. The contributions of homozygous and heterozygous loci were estimated for each plot using the estimators m + a = 2F_2i – F₁ and d = 2(F_2i - F_1i). For NDF, dominance tended to decrease the expression of the trait, though the m + a effect was more significant. The NDMG results were consistent with those for NDF, except for some hybrids in which dominance increased expression of the trait. Genotype × environment interactions contributed a large portion of the total variation, and when the residual was excluded, the R² estimates were 26.95% for m + a, and 33.13% for d for NDF. For NDMG, they were 78.39% for m + a, and 77.63% for d.