Virulence Diversity and Physiological Race Composition of Wheat Stem Rust (Puccinia graminis f.sp. tritici) in Tigray Region, Northern Ethiopia

Abstract

Wheat stem rust (black rust) is one of the most important airborne diseases of wheat (Triticum aestivum) caused by Puccinia graminis f. sp. tritici remains a constraint to the world’s wheat production. Because of the sudden changes in stem rust race patterns, commercial varieties tend to become vulnerable globally at large and particularly in Ethiopia. It was responsible to cause 6.2 million metric tonnes per year or higher losses under severe epidemics at global level. Therefore, this study was initiated to identify the physiological races and virulence diversity of Puccinia graminis f. sp. tritici in Tigray region. Race identification through inoculation of stem rust isolates, multiplication of single-pustule of the pathogen and race designation by inoculating on a set of wheat differential lines were done in the greenhouse. Forty-seven stem rust isolates were analyzed on the twenty stem rust differentials and resulted in the identification of six races namely; TTTTF, TKTTF, TRTTF, TTRTF, RRTTF and TKPTF. In this study, race TTRTF was detected for the first time in Ethiopia during 2017 cropping season. Out of the six races identified, TTTTF was detected from 25 (53.19%) isolates and TKTTF from 15 (31.91%) isolates. The most virulent race that made 18 stem rust resistant genes non-effective was TTTTF, which virulent on 90% of stem rust resistance genes. Differential hosts carrying Sr24 and Sr31 were effective genes which confers resistance to all of the races identified. Hence, the stem rust resistance gene Sr24 and Sr31 can be used as sources of resistance in the wheat breeding program.