ICARDA Achievements in Breeding Spring Bread Wheat Varieties to Resist Stem Rust Race Ug99.

Among wheat production constraints, yield loss caused by wheat rusts is common. Crop losses of 10-60% have been recorded in many countries. Growing of genetically resistant cultivars has been recognized as the most economical and environmentally friendly control strategy. For several decades the problem of wheat stem rust, caused by Puccinia graminis f. sp. tritici, has been controlled through genetic resistance. However, in Eastern Africa, that resistance has been overcome by a new physiological race of the disease designated as Ug99. With its air-borne dispersal mechanism and the long distance travel of rust spores, Ug99 poses a serious threat to global food security. This brought forth strong advocacy for world action from Nobel Laureate Norman Borlaug which led to the formation of the Global Rust Initiative, in 2005, aimed at preventing a pandemic. Since then Ug99 has spread from Kenya to Ethiopia (2005), Sudan (2006) and in a shorter period than expected reached Yemen (2006) and Iran (2008) posing real threat to wheat production in South and East Asia. This presentation highlights the first results of the efforts aimed at combating Ug99 in CWANA by ICARDA/CIMMYT Wheat Improvement Program (ICWIP). These results include improved breeding lines of wheat with diverse sources of both race-specific and complex adult-plant (durable) resistance to race Ug99. This follows 2 years of rigorous field testing at hot spots in Ethiopia, Kenya and Yemen. These lines can now be used in developing and delivering wheat cultivars with durable resistance and other desired characteristics. Additionally, these lines combining resistance and high productivity (>10%) can immediately be deployed as emergency replacement of currently susceptible varieties.