Capacidade combinatória e parâmetros genéticos em cruzamentos de milho

Abstract

The objective of this work was to determine the ability combining of a set of five S5 lines of corn, from landrace populations, as well as to estimate the genetic parameters, and the gene action involved in the genetic control of the main components of the corn crop yield. Two experiments were carried out: in the first experiment, lines obtained from landrace populations cultivated by small producers in the southern region of Rio Grande do Sul were used. The populations were sown in Pelotas - RS, where some plants were self-fertilized until the S5 generation. In the 2017/2018 agricultural harvest, five S5 lines of corn were used, subjected to artificial crosses according to the diallel model, resulting in 20 hybrid combinations. In the 2018/2019 agricultural harvest, the 20 hybrids and five parent strains were conducted in the municipality of Nova Palma - RS, in a randomized block design, with three replications. The ear insertion height, number of ear rows, number of grains per ear row, ear length, ear mass, grain yield and thousand-grain weight were evaluated. In the second experiment, the Planalto and Argentino Branco populations were sown in the 2012/2013 harvest and later crossed to obtain F1’s seeds. F1’s seeds were divided into four fractions. A fraction was stored. In the 2013/2014 harvest, parents and F1’s were sown. The second fraction of F1 seeds was sown and self-fertilized to obtain F2's seeds. The third and fourth fractions were backcrossed (BC) with the parents obtaining BCP1 and BCP2, respectively. In the 2014/2015 harvest, F1’s stored seeds, F2’s, BCP1 and BCP2 and the parents were sown in the field. The following were evaluated: number of ear rows, mass of one hundred grains, mass of ear grains and depth of grains. The CGF_IV strain has a high general combining capacity for ear mass, ear length, thousand grain mass, number of grains in the row and has a reduction in the ear insertion height. The CGF_V strain maximized the mass of a thousand grains and the grain yield. Based on the specific combining ability, crossings CGF_I × CGF_II, CGF_II × CGF_III and CGF_III × CGF_IV are promising for increasing corn grain yield. The study of the reciprocal effect shows that there is no difference when a strain is used as a pollen donor or recipient, since there is no cytoplasmic or nuclear gene effect of the female parent strain on the evaluated characters, under the conditions in which the study was carried out. The additive genetic effect was the most important in determining the traits number of rows in the ear and mass of one hundred grains. However, for grain depth and grain mass, the predominant genetic effect was the additive-additive epistatic interaction. The traits number of rows in the ear, depth of grains, mass of one hundred grains and mass of grains of the ear in corn have quantitative genetic inheritance, with incidence of partial dominant gene action in all of these traits.