Losses caused by stem rust (Puccinia graminis f.sp tritici) on durum wheat in Ethiopia

Stem rust caused by Puccinia graminis f.sp. tritici is one of the major biotic constraints of wheat production. The disease may cause substantial quantitative and qualitative yield losses but much of the work in Ethiopia on this pathosystem focuses on quantitative yield loss of durum wheat. This work was carried out at Debre Zeit Agriculture Research Centre during 2015/16 and 2016/17 main and off-seasons. Hence the current study was conducted with the objectives to quantify the amount of loss in grain yield due to stem rust and assess the relationship between disease parameters, grain yield, and physical quality parameters of improved durum wheat varieties grown in Ethiopia. Artificial inoculation was performed using a mixture of different dominant stem rust races. There were treated and untreated plots by fungicide that serves as protected and unprotected plots, respectively. Disease severity was recorded each 10 days interval and area under disease progress curve (AUDPC), terminal severity, and coefficient of infection were calculated. The tested cultivars exhibited different disease severity levels, having a mean value of 6.7-76%. High values of area under disease progress curve (AUDPC) were detected on Hitossa, Utuba (1225.7, 585.9). Whereas the lowest values of yield loss were recorded on CVS. Mangudo and Utuba have the mean value of yield loss of 40.2 and 44.8%, respectively. The highest yield loss was observed on susceptible variety Hitosa showing the mean value of 70%. Correlation coefficients were tested between yield losses and values of AUDPC, final stem rust severity, coefficient of infection, and rate of infection of the tested cultivars. There were strong correlation coefficients among disease parameters (r=0.72-0.99). There was also a moderately strong negative correlation coefficient among disease parameters and yield, hectoliter weight, and 1000-kernel weight of the test cultivars (r= -0.53 to -0.81). The current study indicated that the application of Rex Duo can be used in minimizing yield losses caused by the stem rust disease of durum wheat. Therefore, supporting the released durum wheat cultivars with fungicide application is the most pertinent issue in Ethiopia as most of the durum wheat cultivars in farmers' hands were moderately susceptible to susceptible cultivars Pgt races.