Identification of physiological race of wheat stem rust (Puccinia graminis f.sp.tritici) and reaction of bread wheat cultivars to emerging dominant races

Abstract

Stem rust is one of the most important foliar diseases of wheat crops. This study was conducted to identify pathogenic variation in wheat stem rust fungus (Puccinia graminis f.sp. tritici) population and evaluation of wheat cultivars to emerging dominant races. For handling diseased samples, major wheat growing areas were selected by multistage sampling technique. Accordingly, 4 zones and 6 districts were selected to get representative disease isolates for race analysis. Hierarchical cluster analysis was done to classify cultivars. Fifty seven single pustules of stem rust were isolated from 86 samples, analyzed using twenty stem rust differentials genes and designated to six races. Among identified races, TKKTF was dominant accounting for 38 % of the isolates followed by TKTTF containing 21.1% of the isolates. TTKTT was the most virulent race identified in current study, 95% of Sr genes susceptible including Sr24, an effective stem rust resistance gene to several stem rust races so far encountered in Ethiopia. The cultivars were classified into 4 hierarchical clusters based on their infection reaction. Among 22 cultivars, four showed low infection type (IT) to race under evaluations. The current statuses of rust race warrants the intimate use of gene edition technology that is a fast track for rust mitigation. Moreover, breeding for stem rust should include screening of resistance genes in wild relatives, wide wheat germplasm to develop varieties tolerant to new and emerging races.