Genotypic Variation in Bread Wheat Under Stem Rust Pressure: Identifying Resistant and High-Yielding Genotypes

Abstract

Stem rust (Puccinia graminis f. sp. tritici) is one of the most destructive diseases affecting wheat production worldwide. Therefore, identifying high-yielding wheat genotypes with resistance to stem rust is essential for sustainable wheat improvement. This study investigated the responses of 18 diverse bread wheat genotypes to stem rust infection under artificially inoculated and protected conditions. The wheat genotypes were assessed for disease-related parameters and their associated impact on agronomic traits. The evaluated traits included phenological characteristics (days to heading), plant growth traits (plant height and flag leaf area), yield components (number of spikes m⁻², number of grains per spike, and thousand-grain weight), grain yield, and biological yield. Moreover, disease-related parameters included disease severity, coefficient of infection (CI), and the area under the disease progress curve (AUDPC). Analysis of variance revealed significant differences among genotypes for all studied traits. Stem rust infection significantly affected the agronomic traits and yield components. It reduced flag leaf area, plant height, grain number, and thousand-grain weight. Disease severity, CI, and AUDPC values varied considerably among genotypes. The susceptible check Morocco exhibited the highest disease severity and AUDPC values. While several genotypes showed moderately resistant reactions across two seasons. ‘Giza-171’, ‘Sakha-95’, ‘Misr-3’, and ‘Sids-14’ exhibited lower disease severity and stable agronomic performance under infected conditions. Multivariate analyses, including hierarchical clustering, principal component analysis, and heatmap visualization, clarified the relationships among genotypes and studied traits. These analyses separated susceptible and resistant genotypes. Genotypes that maintained high yield components under disease pressure were distinguished from those that were susceptible. The agronomic performance and disease resistance analyses identified ‘Giza-171’, ‘Sakha-95’, ‘Misr-3’, and ‘Sids-14’ as promising genotypes. These genotypes combine high productivity with enhanced resistance to stem rust. These promising genotypes represent valuable genetic resources for wheat breeding programs to improve yield and durable resistance to stem rust.