ABSTRACT
Heterosis (or hybrid vigor) is defined in terms of the superiority of F1 performance over some measure of the performance of one or both of its parents. The application of this phenomenon is a multibillion-dollar enterprise manifested in hundreds of millions of hectares of field and vegetable crops throughout the world (usually in terms of yield of grain, fruit, or some aspect of biomass). The use of heterosis represents the single greatest applied achievement of the discipline of genetics, and it is one of the primary reasons for the success of the commercial maize industry as well as the success of plant breeding endeavors in many other crop and horticultural plants. However, the causal factors at the physiological, biochemical, and molecular levels are today almost as obscure as they were at the time of the conference on heterosis held in 1952 (Stuber, 1994, 1999).
