Distribution and virulence diversity of wheat stem rust races (Puccinia graminis f.sp. tritici) in Ethiopia

Abstract

Wheat stem rust (Puccinia graminis f.sp. tritici is the major production constraint of wheat across the globe. Because of the sudden changes in stem rust pathogen race patterns, commercial wheat varieties tend to become vulnerable to the pathogen globally and in Ethiopia particularly. The present study aimed to identify the races of stem rust pathogen and study virulence diversity in Puccinia graminis f.sp. tritici population in the study areas. For this purpose, survey was conducted in 464 wheat fields in the Amhara and Oromia regional states of Ethiopia during 2017 cropping season. During the survey, 60 stem rust-infected wheat samples were collected from the study areas, of which only 48 were viable. Three races of the stem rust pathogen, namely, TKTTF, TTKSK, and TTRTF were identified from 48 isolates. Of the three races, TTRTF is a new race for Ethiopia. Most of the genes possessed by the differentials were ineffective against one or more of the tested isolates except Sr24. The most important resistance gene Sr24 on which the majority of Ethiopian wheat cultivars possess was found to be effective against all races obtained from the study areas. Thus, the use of effective  Sr genes alone or by combining with  other genes would play an important role in providing wheat cultivars with a wider base of stem rust resistance. Frequent tracking of further virulence evolution is recommended to identify the emergency of new races for future breeding programs.

Key words: Phenotype, Race analysis, Virulence evolution, Wheat rust