Wheat stem rust caused by Puccinia graminis f.sp. tritici is amongst the biotic factors which causes up to
100% yield loss during epidemic years. Therefore, the present study was carried out to observe the
reaction of improved durum wheat varieties to virulent stem rust isolates at seedling growth stage and to
stem rust population at adult growth stages. The finding of this experimental study was based on
isolation and multiplication of virulent races of P. graminis, then ten durum wheat varieties including the
susceptible check morocco were tested for the virulent isolates at seedling growth stage; and the reaction of
these varieties under natural field conditions were evaluated in the Eastern and Western Showa of Central
Ethiopia at adult growth stages. At seedling growth stage, 60% of varieties tested with the virulent stem
rust isolate from Debrezeit exhibited resistance, while all varieties were resistant to Ambo isolate. Ten
durum wheat varieties evaluated at adult plant growth stage to stem rust population of Debrezeit (Eastern
Showa) showed severities of 20S in the variety Geredo to 70S in the variety Foka, while at Ambo (Western
Showa) only the susceptible check, Morocco was infected up to 20S. The result indicated that stem rust
from Debrezeit was virulent to durum wheat varieties as compared to the Ambo population.