Evaluation of Kenya Stem Rust Observation Nursery Wheat Genotypes for Yield and Yield Components under Artificial Rust Conditions

Common wheat (Triticum aestivum L.) is a major cereal crop contributing to global food and nutrition which necessitates the deployment of wheat genotypes that are high yielding and resistant to prevailing diseases. The objective of this study was to evaluate Kenya stem rust observation nursery (KSRON) wheat genotypes for grain yield, yield components and stem rust resistance. A 3-season field experiment was set up in a 25 × 7 alpha lattice design at Kenya Agricultural and Livestock Research Organization (KALRO), Njoro (35°56′60′′ E; 0°20′60′′ S). Significant (p ≤ 0.001) differences due to seasons, genotype and genotype × season interaction was observed for all the traits except days to heading (DH) and number of seeds per spike (SS). Seasons, genotype and genotype × season interaction explained 48.2%, 25.23% and 26.67% of the total variability in grain yield (GY), respectively. Significant (p ≤ 0.05) variation of means between seasons for all the traits were higher in the 2019 main season than the 2019 and 2020 off-seasons except for 1000-kernel weight (TKW). Heritability (H²) estimates ranged from 49.58% for GY to 94.11% for DH. GY had a positive genetic and phenotypic correlation with all the traits except for DH (r_g = −0.13, r_p = −0.09), stem rust (SR) (r_g = −0.53 ***, r_p = −0.38 ***) and yellow rust (YR) (r_g = −0.28 ***, r_p = −0.19 *) severity. SR caused 22%, 14% and 13% reduction in TKW, GY and biomass (BM), respectively. YR caused 2% and 4% reduction in GY and BM. This study identified KSRON 13, KSRON 31, KSRON 40, KSRON 52, KSRON 53, KSRON 78, KSRON 80 and KSRON 144 as the best high GY (8.43–7.79 t ha⁻¹) as well as resistant to SR and YR.