Physiological Races of <i>Puccinia graminis</i> f. sp. <i>tritici</i> in Ethiopia in 2019/2020

Abstract

Wheat stem rust caused by <i>Puccinia graminis</i> f.sp <i>tritici</i> is constant biotic constraint of wheat production across the world. Because of quick alteration of genetic makeup of wheat stem rust pathogen; monitoring shift in virulence within pathogen is crucial to avoid sudden occurrence of epidemics due race change. This study was to identify physiological races stem rust pathogen in Ethiopia during 2019 cropping season. Wheat stem rust samples were collected during 2019 main cropping season from major wheat growing areas of Oromia, Amhara, Tigray and Southern Nations Nationalities and Peoples regions of Ethiopia. Besides, samples were also collected from Afar region where wheat was grown by irrigation during off season. The samples where isolated on universally wheat stem rust susceptible line (McNair) for the sake of mono pustule isolation and multiplication to have sufficient spores. Each isolates where inoculated on twenty standard differential lines and each line was evaluated after fourteen days to determine the races. Eight stem rust races namely, TKKTF, TKTTF, TTTTF, TKKTT, TTKTT, TTRTF, TKPTF and TTKTF were identified from samples analyzed; TKKTF was identified from 175 (44.1%) stem rust isolates, while TTTTF was detected from 73 (18.4) samples analyzed. In addition, TKTTF was isolated from 70 (17.8%) samples; however, TTKTF, TTKTT, TTRTF, TKPTF and TKKTT were recorded from 48 (12.1%), 21 (5.3%), 4 (1%), 1 (0.25%) and 1 (0.25%) samples analyzed in the season. TTKTT races have 95% virulence spectra to stem rust resistance genes with in differential lines. Resistance genes (Sr24) that is available in most of commercial varieties worldwide became ineffective with these races. Therefore, breeding program should focus on searching for more sources of resistance to virulent races of the pathogen.