Drought Adaptation in Sorghum
Andrew Borrell, David Jordan, John E. Mullet, Bob Henzell, Graeme Hammer
Abstract
Sorghum has a reputation as a drought-resistant cereal. It is a grass of the steppes and savannas of Africa (Kimber, 2000), and its adaptation to drought is a consequence of its evolution in these arid zones (Doggett, 1988). Sorghum is a repository of drought resistance mechanisms, and has developed biochemical, physiological, and morphological characteristics such as C4 photosynthesis, deep roots, and thick leaf wax that enable growth in hot and dry environments. Sorghum is a warm-season, day-length sensitive grass that is characterized more by diversity than homogeneity (Blum, 2004). The sorghum germplasm collection at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Patancheru, India includes almost 40,000 accessions, which provide a highly diverse and rich source of beneficial alleles (Cui et al., 1995; de Oliveira et al., 1996; Dean et al., 1999; Rosenow and Dahlberg, 2000) for developing drought-resistant genotypes. Remarkable variation in grain type, plant type, adaptability, and productive capacity has been reported (Miller, 1996). Sorghum genotypes may adapt to temperate or tropical climates, high or low altitudes, and too much or too little water (Maunder, 2001; Blum, 2004). Sorghum is the dietary staple of more than 500 million people in more than 30 countries, making it the world's fifth most important crop for human consumption after rice, wheat, maize, and potatoes (Miller, 1996).