Drought is the single abiotic stress with the biggest impact on global crop yields, thus improving crop performance under water-limiting conditions is essential to global food security. This chapter is intended to cover a broad overview of traits and mechanisms known to play a role in drought tolerance in crop plants. Although traditional breeding has largely focused on improving yield under stress-free conditions, a number of mechanisms exist that may be exploited to improve drought tolerance; these include the ABA signaling network for regulation of stomatal movements and root architecture modifications. This chapter reviews the biochemical and molecular modifications induced by water deficit. Stress-induced regulatory genes, specifically involved in marshaling survival responses in metabolism and development, are covered. Traits and genes from tolerant varieties, landraces, and wild relatives, known to contribute to drought tolerance from major crops are also addressed. As our understanding of signaling pathways improves based on studies in models, new traits and opportunities for genetic improvement emerge. Developing varieties that have high yields and are yield-stable in dry environments requires progress in both understanding and applying of genetic and physiological processes. This chapter covers the key traits and genes that have the greatest potential for improving drought tolerance in crop species.
