Characterization of Wheat Yellow Rust Resistance in Bread Genotypes at Adult and Seedling Plant Resistance in South Ethiopia

Yellow rust is the most serious wheat disease in Ethiopia, particularly in highland areas. Field and greenhouse experiments were conducted to characterize the resistance level of bread wheat genotypes to virulent races at seedling and adult plant resistance stages in Ethiopia. A total of 111 advanced Ethiopian bread wheat breeding lines and varieties were characterized under greenhouse and field conditions (two hotspot areas). Seedling resistance characteristics were assessed under greenhouse conditions using three virulent races (PstS2 + v1 + v27, PstS11, and Other/NEW) through artificial inoculations at Kulumsa, and the same entries were used to evaluate resistance under field conditions. In both field experiments, final rust severity, area under disease progress curves, disease progress rate, coefficient of infection, and head infection showed highly significant differences among genotypes. To further understand the relationships among genotypes and key resistance traits, Principal Component Analysis (PCA), cluster analysis, resistance mapping, and correlation studies were performed. PCA identified traits contributing most to genotype differentiation. Cluster analysis grouped the genotypes into four distinct clusters based on their resistance responses. Of the tested genotypes, 58.8% and 10.8% exhibited characterized resistance at seedling and adult plant growth stages, respectively, whereas 4.5% showed resistance at both the greenhouse and two hotspot field areas. Bread wheat genotypes that are resistant at the seedling and adult plant stages to the prevailing races have also been identified. These useful wheat genotypes could be promoted to breeders and farmers after their evaluation for the most important variables, such as yield and reaction to other diseases.