Grain yield is the most important trait in soybeans [Glycine max (L.) Merrill]. It is characterized by quantitative inheritance and high environmental effects. Selection strategies used for development of soybean cultivars could be optimized by the study of the relative importance of the variance components, in particular the proportion of the non-allelic interaction components (epistasis). In order to study the epistatic variation for grain yield in soybeans the "Modified Triple Test Cross" (TTC) method (Jinks et al), was used. Thirty two inbred lines (Pi) derived from a single cross were crossed with two divergent inbred lines (L1 e L2) of the same population and evaluated in 2006/2007 growing season in a triple lattice design (9 replications) with 100 entries: 32 Pi x L1 crosses (L1i), 32 Pi x L2 crosses (L2i), 34 inbred lines (32 Pi plus two testers) and two commercial controls. The variation among the mean contrasts (L1i + L2i - Pi) ) was highly significant in the analysis of variance (P<0.01), indicating the occurrence of epistasis. Results indicate that epistasis can be an important component for the expression of grain yield in soybeans and consequently it needs to be included in the model for the partition of the genetic components of variance.
gene action; variance components; non-allelic interaction; Glycine max
