CAPACIDADE COMBINATÓRIA DE PROGENIES S3 DE MILHO EM TOPCROSSES COM DIFERENTES TESTADORES

Abstract

In maize breeding programs, the selection of partially endogamic progenies is necessary, aiming at the obtainment of superior hybrids. This selection can be based on the estimates of the combining ability, obtained from topcrosses with testers, evaluated by means of diallel analyses. This study aimed at evaluating the genetic merit of S3 maize progenies regarding their combining ability for traits related to the yield and bromatological quality of the forage, as well as grain yield and agronomic traits. Topcross hybrids obtained in crosses from 28 S3 maize progenies with three testers of a narrow genetic base (T1, T2 and T3) were evaluated. The topcross hybrids obtained formed trials topcross 1 (TC1), topcross 2 (TC2) and topcross 3 (TC3), evaluated in independent trials, in crop seasons 2017/18 and 2018/19, in Guarapuava-PR, in a randomized block design, with three replications. In order to select topcross hybrids with a forage purpose, the following were evaluated: dry mass yield (DMY) and the qualitative traits of the forage of the whole plant (WP) and without the participation of the ear (WE), dry mass yield and quality of the grain at the silage point and at the physiological maturation point and agronomic traits of the forage. To select promising topcross hybrids for the production of grains, the agronomic traits and grain yield (GY) were evaluated. The means were subjected to a joint variance analysis, and the genetic parameters were determined, as well as the correlation of the qualitative traits of the forage of the whole plant, without the ear and the qualitative traits of the grain. Progenies 91.1, 106.2, 126.2, 138.1, 152.1, 235.1 and 251.1 are promising for the obtainment of genotypes with high productivity and forage quality, simultaneously. Good quality of the fiber of the vegetative part of the plant can influence the quality of the forage of the whole plant, without depending on only the quality of the grains (greater or lower vitreousness). Progenies 111.2, 131.1, 106.2, 184.2 and 185.1 are promising. Aiming at plant size and grain yield, progenies 61.1, 91.1, 137.1 and 152.1 were selected; it was not possible to select progenies with grain yield and adequate size. The selected progenies must continue in the program, advancing in the endogamy process.