Generation mean analysis in relation to polygenic systems with epistasis and fixed genes

Epistatic effects involving genic combinations of fixed and non fixed genes are shown to contribute to the genotypic mean of any population. These eff ects define specific additive x additive and additive x dominant epistatic components. As such components are not estimable, their relative importance cannot be assessed. These epistatic effects can cause bias in the estimate s of the additive and dominance components to which they are confounded. Th e magnitude of the bias depends on the relative values of the epistatic eff ects, comparatively to deviations d and h, type of prevailing epistasis and direction of dominance.