Prevalence and Pathotype Diversity of Wheat Stem Rust (Puccinia graminis f.sp. tritici) in Eastern Ethiopia

Abstract

Stem rust, caused by Puccinia graminis f.sp. tritici (Pgt) is a major constraint to wheat production worldwide, including Ethiopia. Up-to-date information on stem rust epidemics and pathotype diversity is crucial for effective disease management. This study aimed to assess the prevalence and severity of wheat stem rust and characterise Pgt pathotypes in eastern Ethiopia to support resistance breeding. Disease surveys were conducted across five districts in the East-Hararghe Zone (Girawa, Haramaya, Jarso, Malka Ballo and Meta) and three districts in the West-Hararghe Zone (Gamachis, Masela and Tulo) during the main cropping season. A total of 44 wheat fields were surveyed, and 27 stem rust samples were collected. Pathotyping was performed at the Ambo Plant Protection Research Center using 20 North American differential lines. Stem rust was detected in 77.3% of the surveyed fields, with varying disease severity. Five Pgt pathotypes were identified: TKKTF, TTTTF, TKTTF, TKPTF and TTKTT. Notably, the recently detected TTKTT race exhibited virulence against 95% of wheat genotypes, including those carrying the Sr24 resistance gene. This race was isolated from the widely grown variety Ogolcho in the Jarso district. The findings highlight eastern Ethiopia as a hotspot for wheat stem rust, harbouring genetically diverse and highly virulent pathotypes. The insights from this study provide valuable information for targeted disease screening and resistance breeding efforts in Ethiopia and beyond.