The genetics of corn breeding

Hybrid corn has now replaced open-pollinated varieties almost completely. This change-over has been accompanied by a nearly 3-fold increase in U.S. average yields. The genetic basis for corn breeding rests upon classical Mendelian concepts. On this base has been built a quantitative approach which uses variance components to characterize population and environmental effects. Appropriate models permit separation of genetic effects into additive, dominance, and epistatic components and their interactions. Knowledge concerning the relative magnitude of these effects has been used both to provide a more complete genetic understanding of the early procedures used and to develop new, more efficient breeding procedures. This paper attempts a brief historical review of these genetic developments.G. F. SPRAGUE, United States Department of Agriculture, Plant Science Research Division, Beltsville, Maryland