Epistasis, or non-allelic interaction, may be of considerable importance in the inheritance of quantitative traits in soybeans . Hanson and Weber (1962) and Hanson et al. (1967) used a nested progeny design to partition the genetic variance among homozygous lines into additive and additive x additive (epistatic) components . In each of two populations, approximately 70% of the genetic variance for grain yield was attributable to epistasis.