Genetic analyses of agronomic traits in F4:3[8] and F5:3[8] progenies derived from eight-parent soybean crosses

O.T Hamawaki,F.C Juliatti,N.A Vello

doi:10.12702/1984-7033.v02n02a13

Abstract

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 F 4:3[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 F 4:3[8] progenies were evaluated in an augmented block design in the 1994/95 growing season. The F 5:3[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 progenies in some crosses allowed the prediction of additional gains for grain yield through selection in more advanced cycles.

Highlights

Soybean (Glycine max (L.) Merrill] is an oilseed plant cultivated for more than 5,000 years, and has become the staple food of the Chinese people, a habit influenced by its availability after domestication in Northeast China (Hymowitz, 1970)
There is general consensus among the majority of specialists that the most likely primary center of genetic diversity of the species is the Central-Southern region of China with a secondary center in Manchuria
The utilization of exotic germplasm was suggested by Vello (1985) as a strategy to widen the genetic base of the Brazilian soybean cultivars

Summary

Introduction

Soybean (Glycine max (L.) Merrill] is an oilseed plant cultivated for more than 5,000 years, and has become the staple food of the Chinese people, a habit influenced by its availability after domestication in Northeast China (Hymowitz, 1970). The utilization of exotic germplasm was suggested by Vello (1985) as a strategy to widen the genetic base of the Brazilian soybean cultivars. The genetic background of the Brazilian cultivars is very narrow, since their genealogy traces back to only 26 ancestors, 11 of them contributing with 89% of the total gene pool (Hiromoto and Vello, 1986). Six of these ancestors are the most frequent genotypes found in the genealogies of the Northern American cultivars. Six of these ancestors are the most frequent genotypes found in the genealogies of the Northern American cultivars. Vello (1985) suggested that a proportion of 25% of selected exotic germplasm should be gradually introduced into the cultivated germplasm, through triple crosses or using populations with a wide genetic base

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