Population Genetics of Increased Hybrid Performance between Two Maize Populations under Reciprocal Recurrent Selection

Heterosis, the superiority in one or more characteristics of crossbred organisms relative to their inbred parents, is the basis of the modern cultivars utilized in maize. The two genetic mechanisms most commonly invoked to explain heterosis are dominance and overdominance. For maize and certain other domesticated species that employ inbred lines to produce commercial hybrids, knowledge of the mechanisms of gene action producing heterosis could contribute to advances in breeding techniques. In theory, reciprocal recurrent selection (RRS) is intended to improve the performance of an interpopulation cross of two genetically divergent populations. Two maize populations, Iowa Stiff Stalk Synthetic (BSSS) and Iowa Com Borer Synthetic #1 (BSCBl), are currently in their 14th cycle of RRS in the Cooperative Federal‐State maize breeding program at Iowa State University. The use of molecular markers has provided some insight into the roles of selection and genetic drift in BSSS(R) and BSCBl(R).