Maize Heterosis

In maize breeding, heterosis is quantitatively assessed as the excess of F1 hybrid performance over the arithmetic mean of the parents or the performance of the superior parent. To predict cross effectiveness, breeders analyze the General Combining Ability (GCA) of lines, which determines their average merit, and the Specific Combining Ability (SCA), which reflects deviations in specific hybrid combinations.

The heterosis effect in maize allows for a 20–30% or greater increase in grain and biomass yield, while improving ear size, kernel filling, and resistance to stress factors. To maximize hybrid vigor, breeders use the classification of inbred lines into heterotic groups, such as Stiff Stalk, where crossing between groups provides the best performance.

Since the maximum effect of heterosis is observed exclusively in the first generation, only specialized F1 hybrid seeds are used for commercial maize cultivation. In subsequent generations, there is a predictable decline in plant productivity and vigor.