Exploitation of Heterosis: Uniformity and Stability

Crop uniformity is considered a desirable character in modem agriculture because product uniformity is essential in marketing; uniformity in maturity permits crop scheduling; and uniformity in plant structure and maturation permits efficient mechanical harvest. Crop uniformity is associated with a lack of diversity but diversity can be increased by planting a number of different homogeneous cultivars. Production of F 1 hybrids of seed‐propagated crops is a successful breeding technique because it exploits heterosis, promotes homogeneity in allogamous species, and is a way for commercial breeders to control their product. There are two dimensions to the uniformity of hybrids: genetic homogeneity and genetic stability. Techniques to maximize genetic progress for crop yield must include selection for both yield performance and stability from the earliest segregating generations. The maize industry in the USA has shifted to single‐cross hybrids to maximize yields and increase uniformity.