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

The objective of the present study was to evaluate 44 soybean octuple cross es in the F-4:3[8] and F-5:3[8] generations in order to select progenies su perior for seed oil yield (OY) and other important agronomic characteristic s. Octuple crosses were hybridized in a chain mating system. In one group, crosses were carried out for three generations with the adapted x exotic pa rents until octuple crosses with 75% adapted genes and 25% exotic genes wer e obtained. In a second group, hybridization of adapted x adapted parents o riginated crosses with 100% adapted genes. During the growing season 1994/9 5, the progenies F-4:3[8] were evaluated by using the augmented block desig n. The progenies F-5:3[8] were evaluated during the growing season 1995/96 in three experiments using augmented block design without repetition. The o ctuple crosses gave origin to superior progenies for all the characters stu died. In the C22 cross, OY values were 707 kg/ha. The estimates of heritabi lity in relation to the crosses average resulted in the following mean, min imum 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 ear ly, intermediate and late F-5:3[8], progenies were superior to the expected genetic gains and the observed genetic gains for OY were more expressive i n the early and late F-5:[8] progenies. The genetic variability remaining i n the selected progenies of some crosses suggests that further genetic gain s for grain yield and OY might be possible with advanced selection cycles.