Selection of Stable Cultivars Using a Safety‐First Rule

The presence of genotype by environment interaction is of major concern to plant breeders, since large interactions can reduce gains from selection and complicate identification of superior cultivars. Numerous statistics have been proposed to characterize stability of cultivars, yet none of these methods explicitly indicate how stability may be combined with mean yield in choosing superior cultivars. It is assumed that the plant breeder prefers a cultivar with a small probability of low yield. Using a decision‐theory concept known as safety‐first to model such behavior, an index incorporating mean yield and stability is developed for each of four different definitions of stability. Data from an international experimental maize ( Zea mays L.) yield trial are used to illustrate the application of these indices when genotype by environment interaction is present. It is concluded that safety‐first selection indices can be useful to plant breeders when genotype by environment interaction is large and poor yield has severely adverse consequences.