Responses to divergent selection for cob color in maize

Previous studies showed that in materials derived from maize (Zea mays L.) single cross A632 × Mu195 there is association between agronomic traits and cob color (affected by P1 gene). Objectives of this study were to evaluate the responses to divergent selection for cob color in F₂-Syn 0 (obtained by selfing A632 × Mu195), estimate the genetic parameters of the involved putative quantitative trait loci (QTL), and evaluate the responses to divergent selection for cob color in A632 and Mu195 backgrounds. The populations selected in F₂-Syn 0 for red (R0) or white cob (W0) were tested in four trials. Differences between R0 and W0 were found for grain yield (85.0 vs. 75.0 g/plant) and other traits; most of these differences were related to leaf number/plant. Then, population F₂-Syn 1, derived after one random mating generation, was divergently selected for cob color, thus producing R1 and W1. Populations R0, W0, R1, and W1 were tested in two trials, allowing the estimate of genetic effects and recombination frequencies for putative QTL of several traits. Finally, a divergent selection for cob color was conducted in segregating materials of A632 and Mu195 backgrounds. The two pairs of selected populations were compared in two trials; the responses were similar to those detected by comparing R0 and W0. We conclude that divergent selection for cob color in F₂-Syn 0 is effective for several traits, that such responses are due to putative QTL linked to P1, and that selection is also effective in different genetic backgrounds.