Evaluation of Resistance of Some Iranian Spring Bread Wheat Cultivars to Stem Rust Disease at Seedling Stage

This study aimed to evaluate the resistance of 58 spring bread wheat cultivars to stem rust at seedling stage. For this purpose, four races of stem rust pathogen; TTTTF, PTRTF, TTKTK, and TKTTF, which are among the dominant races of stem rust disease in Iran, were used. In all experiments, Morocco and McNair cultivars were included as susceptible controls. Based on the reaction of cultivars, no resistance was observed against all races, and only three cultivars; Adl, Dez, and Ofogh were resistant to three different races of the four races of stem rust pathogen. The results showed that 12 cultivars had resistance against TTTTF and TTKTK, 10 cultivars against PTRTF, and seven cultivars against TKTTF, with reaction on scale of "0" to "2+". Cluster analysis using the Ward’s method classified the studied cultivars into five different groups ranging from resistant, moderately-resistant, medium, moderately susceptible, and susceptible reactions for each race. Principal component analysis revealed that cvs. Sivand, Pishtaz, Adl, Niknejad and Ofogh had resistance to TTTTF and PTRTF, and cv. Kaveh showed resistance to TTKTK and TKTTF. Resistance reactions observed in these cultivars may be due to unidentified gene (s) that have not been affected by the pathogen races used in this study. The information about the reaction of spring bread wheat cultivars to stem rust pathogen races at seedling stage can be invaluable for wheat breeders for incorporating stem rust resistance sources in bread wheat breeding programs. Of course, the reaction of spring bread cultivars to stem rust pathogen races at adult plant stage should also be evaluated and considered.