ABSTRACT
Rice is the most important food crop in the world. Rice accounts for more than 40% of caloric intake in tropical Asia, reaching more than 60% in many countries and for many poor people. During the past 35 years, world rice production doubled as a result of the adoption of modern varieties and improved cultural practices. It is estimated that world rice production has to increase by 1 % annually in the next 20 years to meet the growing demand for food (Rosegrant et al., 1995). It is a big challenge to continuously increase world rice production at such pace since the production environment will be very different from those in the past. Rice productivity is showing signs of decline, expansion of area is limiting, investments in irrigation have virtually ceased, high fertilizer use is causing concern, and good rice lands are being lost to other purposes. The only option available is to raise rice yield potential in favorable environments and to enhance adaptability of rice cultivars in less favorable environments through genetic improvement.
