9 - World Distribution in Relation to Economic Losses

Abstract

Publisher Summary Two-thirds of the world's total food supply is comprised of eight major cereal crops: wheat, rice, barley, rye, oats, corn, sorghum, and pearl millet. These crops may include more than one plant species, and the Food and Agriculture Organization (FAO) production statistics are often for total production. The millets are the most diverse group, being made up of several plant genera. In addition to the cereal crops, sugarcane is recognized as a major contributor to the world's food supply. Wheat and barley are grown primarily as temperate crops with a small area sown in the subtropics at present. A diverse virulence spectrum exists for both bread wheat and durum wheat. The leaf rust of wheat consistently causes some production losses but never as severe as the losses that are associated with stem rust. At present, the commercially grown spring bread wheat and durum wheat cultivars have adequate resistance to prevent severe losses. However, shifts in the virulence patterns of the pathogen continue to be of concern. Most winter wheat cultivars are at present susceptible to at least a part of the pathogen population.