Abstract only

Race Ug99, or TTKSK, of fungus Puccinia graminis f. sp. tritici, causing stem or black rust disease on wheat (Triticum aestivum) has been recognized as a major threat to wheat production. First detected in Uganda in 1998 and now spread throughout East Africa, Yemen, Sudan and Iran, with further predicted spread towards North Africa, Middle East, Asia and beyond, has raised serious concerns of major epidemics that could destroy the wheat crop in various areas. Detection of two new Ug99 variants, TTKST and TTTSK, in Kenya in 2006 and 2007 with virulence to genes Sr24 and Sr36, respectively, also show that Ug99 is evolving. The TTKST variant caused severe epidemics in 2007 in the southern region of Kenya on the Sr24 carrying variety Kenya Mwamba and rendered about half of the previously known Ug99-resistant global wheat materials susceptible. This has further increased the vulnerability of wheat globally. Rigorous screening since 2005 in Kenya and Ethiopia of wheat materials from 22 countries and International Centers has identified resistant materials, although in low frequency, that have the potential to replace susceptible cultivars. Diverse sources of adequate resistance, both race-specific and adult-plant type, are now available in improved wheat backgrounds and are being used in breeding worldwide. Ug99 threat in most countries can be reduced to low levels by urgently identifying, releasing and providing to growers seed of new high yielding, resistant varieties. The Borlaug Global Rust Initiative (BGRI) was launched in 2005 to build international partnership, raise awareness and financial resources, develop and implement research and developmental priorities to mitigate the threat from Ug99. The consortium has been very successful in achieving these objectives and provides a model for tackling global issues including the threat posed by the yellow rust pathogen. Strong partnerships among and between institutions in developed and developing countries, and international centers will be necessary to bring long-term control of rust diseases in innovative ways through a better pathogen surveillance, development of critical screening sites and facilities, higher emphasis on the use of multiple minor genes in breeding varieties with nearimmune levels of resistance, identifying new sources of race-specific resistance genes and their deployment in combinations aided by marker-assisted breeding, and simplifying breeding by developing multiple resistance genes carried in cassettes following their cloning.

Text in English