Theoretical maximum contribution of dominance complementation to heterosis

Heterosis refers to the superiority of F1 hybrid over its inbred parents. Although heterosis has been widely used in the production of maize and rice, its genetic basis remains a matter of conjecture. Without the roles of overdominance and/or epistasis in heterosis, elite hybrids would finally lose their advantage over inbred lines possessing the vast majority of superior alleles. Here we demonstrate the theoretical maximum contribution of dominance complementation to heterosis with a focus on diploid plants, and compare our theoretical results with the experimental observations. The comparisons indicate that the theoretical maximum contribution of dominance complementation to heterosis is inadequate to explain heterosis exhibited by the elite maize hybrids and cannot be reached by the actual contribution of dominance complementation to heterosis. The gap between heterosis and the actual contribution of dominance complementation to heterosis in the elite maize hybrids should be attributed to the roles of overdominance and/or epistasis in heterosis. These findings imply that the advantage of elite hybrids over elite inbred lines can be maintained even when the vast majority of superior alleles accumulate in inbred lines.