ABSTRACT The production of green maize is considerable important for various regions of Brazil. It is vital that breeding programs of public institutions seek to meet the needs of this market sector, which has a relevant social role, mainly on small properties. The aim of this study was to estimate the inbreeding depression and the genetic components (m + a and d) of characters associated with green maize production and quality in three populations of different genetic basis: the variety UFG-Samambaia (P1), and two populations formed by crossing the commercial hybrids (P2 e P3). The S1 progenies of each population, the three S0 populations, and two checks were evaluated in a 14 × 14 triple lattice design. Agronomic and ear quality traits were evaluated. Genetic variability and greater inbreeding depression were observed for most of the traits among the P1 progenies. In P2 and P3, greater inbreeding depression was observed for male flowering, ear weight without straw, ear diameter, ear weight, female flowering, breakage and lodging, and grain color. The traits of ear quality, important for green maize production, had greater inbreeding depression than the agronomic traits, indicating that inbreeding depression and exploitation of heterosis should be considered in the selection process for these traits.

Abstract Diallel designs are widely used in plant breeding to select parents and to study trait inheritance. The present work aimed to present a method to evaluate two divergent groups of parents, in which one group is used as a tester of the contrasting group. Each parent is crossed with a balanced mixture of seeds from the parents of the other group, and the parents and topcrosses are experimentally evaluated. Two groups of ten inbred maize lines were used to obtain intergroup topcrosses and biparental crosses in a diallel scheme. The data were subjected to analysis of variance and parameter estimation using the two models. The results showed the reliability of the method for the evaluation of lines and prediction of means of hybrid populations and can be recommended when the number of parents to be evaluated is large, making it difficult to evaluate biparental crosses in a diallel scheme.

Abstract Topcrosses are routinely used in maize-hybrid programs. This study aimed to evaluate heterosis components and combining ability to predict hybrid means between synthetics from two groups of S1 maize lines using the intergroup topcrosses model that includes S2 lines. Two groups, each with 30 S1 maize lines, were crossed using an intergroup topcross system, with a mixture of lines from one group as a tester for the contrasting group. Simultaneously, 30 S2 lines from each group were generated via self-pollination. Lines and topcrosses were experimentally evaluated and the data were analyzed using a model adapted to the study design. The results showed the suitability of the proposed model for studying heterosis components and general combining ability, detailing additive and dominance effects. Prediction of hybrid means between synthetics showed the potential of the lines to generate base populations for an interpopulation breeding program.