A new explanation for egg production heterosis in grosses between white leghorns and australorps

Abstract

1. Present population genetics theory treats heterosis as the reversal of inbreeding depression. This theory is not generally applicable to heterosis occurring in crosses between different breeds or between unrelated strains of the same breed. 2. Heterosis occurring in such crosses is explained in terms of different complementary epistatic gene pathways homozygous in the parental breeds. 3. In the absence of linkage, these epistatic gene pathways segregate in the second and subsequent cross‐bred generations leading to the loss of the heterosis observed in the first cross‐bred generation.