Improvement in genetic characteristics and oil yield of selected soybean progenies from octuple crosses

Abstract

The objective of the present study was to evaluate 44 soybean octuple crosses in the F4:3[8] and F5:3[8] generations in order to select progenies superior for seed oil yield (OY) and other important agronomic characteristics. Octuple crosses were hybridized in a chain mating system. In one group, crosses were carried out for three generations with the adapted x exotic parents until octuple crosses with 75% adapted genes and 25% exotic genes were obtained. In a second group, hybridization of adapted x adapted parents originated crosses with 100% adapted genes. During the growing season 1994/95, the progenies F4:3[8] were evaluated by using the augmented block design. The progenies F5:3[8] were evaluated during the growing season 1995/96 in three experiments using augmented block design without repetition. The octuple crosses gave origin to superior progenies for all the characters studied. In the C22 cross, OY values were 707 kg/ha. The estimates of heritability in relation to the crosses average resulted in the following mean, minimum and maximum values, respectively: number of days to maturity (52.35%, 3.71%, 84.23%); agronomic value (26.69%, 1.62%, 61.28%) and grain yield (29.28%, 1.52%, 61.06%). The observed genetic gains for grain yield in the early, intermediate and late F5:3[8] progenies were superior to the expected genetic gains and the observed genetic gains for OY were more expressive in the early and late F5:[8] progenies. The genetic variability remaining in the selected progenies of some crosses suggests that further genetic gains for grain yield and OY might be possible with advanced selection cycles.