Breeding crop varieties for stress environments

Plant stress is a major limitation to crop yield. The amelioration of crop environments is either impossible or costly. The breeding of crop varieties resistant to environmental stress is the most effective economical means to improve and stabilize yield under conditions of stress. Crop resistance to various environmental stresses is being improved by traditional and costly breeding methods that involve the stability of yield performance over different environments as a major criterion. Recent advances in stress physiology allow embarkation upon breeding programs that employ distinct physiological selection indices for stress tolerance. Using physiological selection indices in breeding work requires the definition of the importance and effectiveness of given physiological attributes under stress conditions, the design of a proper selection scheme within the logistic framework of the breeding program and the development of rapid and effective selection techniques. These requirements, the progress made and the future prospects are discussed for tolerance to drought, suboptimal temperatures, supraoptimal temperatures, salinity and mineral deficiency or toxicity stresses.