Corn Breeding: Types of Cultivars - Summary
Important types of corn cultivars are inbreds, single-cross hybrids, double-cross hybrids, and various kinds of populations. Differences among these types can be understood in terms of their genetics. For example, among these types only inbreds are pure-breeding. Any inbred has this characteristic because it is homozygous at all loci.
A hybrid is a cross between two genetically different plants. The most prevalent type of cultivar grown by U.S. farmers today is the single-cross hybrid. A single cross is produced by crossing two inbreds.
Corn hybrids generally are more vigorous than their parents. This increase in vigor is called hybrid vigor. When two inbreds are crossed that are not closely related, considerable vigor in plant and ear size relative to the parental inbreds is often observed in the single-cross hybrid. Usually a lesser amount of hybrid vigor is observed in other types of hybrids, such as a population x population hybrid or a population x inbred hybrid