First Report of a Puccinia graminis f. sp. tritici Race Virulent to the Sr24 and Sr31 Wheat Stem Rust Resistance Genes in South Africa

Isolates of Puccinia graminis f. sp. tritici belonging to the Ug99 race group are virulent to a broad spectrum of resistance genes, rendering most of the world's wheat germplasm susceptible to stem rust (3). Following the initial detection of Ug99 (TTKSK, North American [NA] race notation) in Uganda, virulence to the widely used Sr31 resistance gene has been reported from Kenya, Ethiopia, Sudan, and Iran (2,3). In November 2009, a wheat genotype suspected to carry Sr31 showed a susceptible response to stem rust in a disease nursery (29°08′05.02′′S, 30°38′29.18′′E), inoculated with race TTKSP, near Greytown in KwaZulu-Natal, South Africa.