This chapter introduces the reader to the important concepts of stability and stability-related statistics. The myriads of stability statistics that have been developed are briefly mentioned. The point is emphasized that genotype-by-environment interaction (GEI) is a breeding issue and is appropriately dealt with in breeding programs. Strategies are outlined for handling GEI in plant breeding. The genotype and genotype-by-environment (GGE) biplot method is introduced and its versatility and merits are briefly discussed.

GEI has been a continuing challenge for breeders and has significant implications in both applied plant and animal breeding programs (Kang, 2002). Breeders have found the GEI issue to be intriguing and perplexing because there is no uniform way to handle GEI and usefully integrate it into breeding programs (Kang, 1990; Kang and Gauch, 1996; Cooper and Hammer, 1996).

GEI has led to the development of concepts of stability or consistency of performance. In the next section, the various concepts of stability and stability statistics are discussed.