New virulence in East Africa In a nursery in Uganda, Africa in 1999, susceptible type stem rust pustules (collection designated Ug99) were found on wheat lines known to have the stem rust resistance gene Sr31, a gene for which no virulence had been reported previously anywhere in the world.  Similar virulence was observed in 2001 in Kenya and 2003 in Ethiopia.  (Race identification of earlier observations prior to 2001 could not be confirmed because of a lack of samples).  Race typing (race TTKS based on Pgt system of nomenclature, see Phytopathology 78:526-533) and DNA confirmed the presence in Kenya in 2005.  Sr31 is on the 1B/1R chromosomal translocation, a piece of rye chromosome that has been introduced into many wheat cultivars.  In addtion to Sr31, the leaf rust resistance gene Lr26 and the stripe rust resistance gene Yr9 are also on the 1B/1R translocation. Stem rust vulnerability of wheat worldwide--the Sr31 factor Stem rust resistance gene Sr31 is widely utilized in wheat worldwide, particularly in the India subcontinent, China, Europe, and South America.  From the CIMMYT report: Impacts of International Wheat Breeding Research in Developing Countries, 1966-97, developing countries planted 69 million hectares (~170 million acres) of spring wheat in 1997, of which nearly 80% were planted to CIMMYT-related varieties.  Susceptibility of this material will provide little barrier to the spread of a virulent race (e.g. TTKS).