Evaluation of Adult Plant Resistance in Bread Wheat (<i>Triticum</i><i> </i><i>aestivum</i> <i>L</i>.) Genotypes to Wheat Stem Rust (&

A field experiment was conducted during the 2021 main cropping season using an augmented design to evaluate adult plant resistance in bread wheat genotypes against wheat stem rust (Puccinia graminis f. sp. tritici) in Ethiopia. Final rust severity (FRS), coefficient of infection (CI), and relative area under the disease progress curve (rAUDPC) were used to identify slow rusting genotypes. These parameters proved reliable for assessing resistance. Eleven Pgt races were tested on 20 near-isogenic lines carrying single stem rust resistance genes. Greenhouse results showed seven lines were resistant to all races. Genotypes were grouped based on infection types: Group I (e.g., genotypes 40 and 56) showed low infection types (ITs); Group II (e.g., genotypes 2, 3, 12, 13, 43, 91, 98) showed high ITs; Group III included 68 lines with variable reactions. TTKTF and TKPTF caused the highest ITs, while TTKTT showed the lowest. Thirty slow rusting genotypes were identified based on field FRS (Trace MS to 25 MS) and seedling ITs (2+ to 4). These cultivars offer valuable genetic resources for wheat improvement programs targeting durable resistance to stem rust. These findings demonstrate the importance of combining field-based slow rusting parameters with greenhouse race-specific evaluations to obtain a comprehensive understanding of resistance. The identification of genotypes with stable resistance across multiple environments provides a strong foundation for breeding programs aimed at durable stem rust resistance. Such cultivars are particularly valuable in Ethiopia, where stem rust epidemics pose a recurring threat to wheat production and national food security. This study contributes to the global effort of developing improved wheat varieties by offering genetic resources that can be integrated into international breeding pipelines. By highlighting both race-specific and slow rusting resistance, the research underscores the need for continuous monitoring of pathogen variability and the deployment of diverse resistance genes to ensure long-term effectiveness.