Wheat stem rust in South Africa: Current status and future research directions

Plant diseases are among the major causes of crop yield loss and food insecurity. In South Africa, stem rust caused by Puccinia graminis Pers. f. sp. tritici. Eriks. & E. Henn. (Pgt) is an important disease of wheat. Records of stem rust occurrence in South Africa date back to the late 1720’s, when it was first discovered in the south-western wheat growing areas of the Western Cape. Although growing stem rust resistant cultivars is one of the most economic and environmentally feasible strategies, one of the challenges in host-plant resistance is that Pgt frequently acquires new virulence to overcome resistance genes in existing cultivars. There is strong evidence that the pathogen continues to evolve through mutation and genetic recombination. The appearance of stem rust race Ug99 (TTKSK, North American race notation) in East Africa in 1999 and subsequent epidemics in Kenya and Ethiopia was accompanied by the occurrence of four Ug99 variants (TTKSF, TTKSP, PTKST and TTKSF+) in South Africa. These have resulted in a renewed interest in understanding the status of Pgt races and stem rust resistance in the world as well as the need for a new host-plant resistance strategy. The current review summarises up-to-date literature on the prevalence of stem rust races in South Africa, and also draws attention to the resistance genes and strategies currently deployed to combat this disease. The aim of the review was to provide perspectives on research milestones and guide future research programs for reducing losses incurred by stem rust of wheat in South Africa.Keywords: Durable resistance; Pathogen variability; Puccinia graminis f. sp. triticiAfrican Journal of Biotechnology, Vol 13(44) 4188-419