Analysis of heterosis by a direct method using the concept of heritability

The presence of heterosis has been observed in many species at both phenotypic and gene levels. Strangely, the genetic basis of heterosis was and still is largely unknown. In this study, we extended and simplified some formulas that we reported previously. The foundation of our model was based on partitioning the F1 phenotypic variance of the cross between two pure lines into additive, dominance and epistasis components, which lead to the estimation of effective factors, crossheritability in the broad and narrow sense and heterotic power. In the model, we assume that all polygenes controlling a quantitative trait have an equal genetic effect and are independent of each other. By extension of the heritability to a cross population, new features appear. The word 'crossheritability' acquires the status of a new genetic parameter that suffices to deal with the problem of crossbreeding and clarifies the picture of heterosis. Lastly, an example of employing the proposed method in analyzing the crossing data from Drosophila melanogaster is given to illustrate its application.