ABSTRACT
Drought, salinity, and flooding are the major abiotic stresses that limit crop production all over the world. Drought is, by far, the leading environmental stress in agriculture in the United States and the rest of the world. Most of the crop production areas of the world face frequent and short periods of water deficits almost every year and severe drought stress in some years. Drought at any stage of crop development affects growth and production, but drought during the flowering stage causes maximum crop damage. Drought is endemic in large areas of Asia and Africa, where most of the world’s poor people live and where they fully depend on rainfall for crop production. The developed world is not exempt from the problem. In the United States alone, about 40% of crop losses occur yearly due to drought (Boyer, 1982). Efficient irrigation systems can mitigate crop loss due to drought and can also bring more areas under cultivation. However, the increasing cost of irrigation water is a great concern for profitable crop production, especially for poor farmers in sub-sistence agriculture. All over the world, most of the cereal crops are grown under rainfed conditions where irrigation is unavailable or, if available, too costly for marginal farmers. Under a water-limited environment, the genetic improvement of a crop for drought resistance is a sustainable and econom-ically feasible solution to reduce the problem of drought (Blum, 1988).
