Development of wheat germplasm for stem rust resistance in eastern Africa

Abstract

Wheat (Triticum aestivum) rust outbreak is the primary production constraint in Eastern Africa. Ethiopia, Kenya and Uganda are hot spots for the epidemic of rusts, due to higher rates of evolution of new pathogen races, especially of the virulent stem rust (Puccinia graminis) race, Ug99. The objective of this study was to identify sources of resistance to the major pathotypes of stem rust prevalent in some countries of Eastern Africa. Three hundred and six elite breeding lines, selected and advanced at the Wheat Regional Centre of Excellence (WRCoE) in Ethiopia, were planted in stem rust hot spot areas of the country (Arsi-Robe) and Kenya (Njoro) under natural infections. Stem rust scores of 18, 25.8 and 56.2% of lines at Arsi-Robe; and 35, 49 and 16.7% of lines at Njoro were resistant to moderately resistant, intermediate and moderately susceptible to susceptible category, respectively. Overall coefficient of infection (ACI) at Arsi-Robe (24) was greater than that of Njoro (13), indicating higher disease pressure in Ethiopia than Kenya. Among the lines, 67% at Njoro and 49% at Arsi Robe showed good levels of resistance, with a severity less than 20%. However, only 32% of the lines showed a good level of resistance (<20% severity) in both locations. These lines could have combined resistance to the multiple stem rust races prevailing at both locations. Generally, most of the lines, which showed better resistance at Njoro were susceptible at Arsi-Robe.

Key Words: Hot spots, Puccinia graminis, Triticum aestivum