The cultivation of barley is nearly as old as the origin of agriculture, dating back over 10,000 BP (recent reviews by Fischbeck, 2002; Molina-Cano et al., 2002). Since its domestication in the Near East fertile crescent (Zohary and Hopf, 1994), and possibly in two other regions of the world (Zohary, 1999; Molina-Cano et al., 2002), this neolithic crop has spread over a large part of the world from Siberia to Chile. The crop now covers over 64 million ha of cultivated land (FAO, 2003). In the Near East center of diversity, barley is grown primarily as a winter cereal. Much of the 5 million ha of land under barley in this region is subject to one or more stresses. In these regions, barley is typically grown on marginal land, leaving more favorable cropland to wheat cultivation (Ceccarelli, 1984). Because of frequent drought and high temperatures in the growing season, genetic adaptation to adverse growing conditions has been an important determining factor for barley’s success as a major field crop.