Genetic analyses of agronomic traits in F4:3[8] and F5:3[8] progenies derived from eight-parent soybean crosses
Osvaldo Toshiyuki Hamawaki; Natal Antonio Vello and Fernando César Juliatti
The utilization of exotic germplasm comprises a strategy for improving the genetic diversity within soybean cultivars, whose present narrowness is a main limitation in soybean breeding programs that utilize two-way crosses between homozygous pure lines. Progenies from forty-five soybean crosses obtained through the combination of eight parents (octuple crosses) in a chain mating system were evaluated in the F4:3[8] generation for grain yield and other agronomic important traits. The octuple crosses included both adapted and exotic parents mated in a chain system during three generations to assemble a group of materials with the proportion of 75% : 25% of genes stemming from adapted and exotic parents, respectively. In addition to this, adapted parents were selected to form a second group with 100% adapted germplasm. The F4:3[8] progenies were evaluated in an augmented block design in the 1994/95 growing season. The F5:3[8] progenies were evaluated in six experiments during the 1995/96 growing season. Three augmented block designs (without replications) and three complete randomized- block designs with two or three replications were used. The analyses of the results indicate that octuple crosses produced superior progenies for all the traits studied, especially grain yield which presented the excellent mean yield of 5.530 kg/ha. Remnant genetic variability amongst selected progenie