Stem rust and yellow rust are major diseases of wheat (Triticum aestivum L.) caused by Puccinia graminis and Puccinia striiformis, respectively. In Kenya, although the two diseases occur together, available genetic resistance is limited. Therefore, research for resistance to both diseases is of priority. We therefore evaluated 59 Australian wheat genotypes alongside local checks over three seasons in Njoro, Kenya, for resistance to stem rust, yellow rust and yield performance and one season in Debre Zeit, Ethiopia, for resistance to stem rust in a partially balanced lattice-square design with three replicates. Resistance to stem rust isolates TTKSK and TTKTT was evaluated in the greenhouse. Effect due to genotype, season and genotype-by-season interaction was significant (p ≤ 0.05) for area under disease progress curve (AUDPC), coefficient of infection (CI), final disease severity (FDS), grain yield (GY), 1000-kernel weight and test weight (TW). AUDPC, CI and FDS were negatively correlated with GY and TW. Broad-sense heritability (H2) for AUDPC, CI and FDS was 70.2, 60.0 and 68.1% for stem rust and 55.8, 50.0 and 59.7% for yellow rust, respectively. Genotypes Lancer, Sunguard and Gauntlet exhibited stable resistance to stem rust in Njoro and Debre-Zeit while genotypes Sunmax, Steel and Gladius showed stable resistance to yellow rust in Njoro. Genotypes Lancer, Sunguard, Gauntlet, Sunmax, Steel, Gladius, Shield and Magenta, having adult plant resistance to stem rust and yellow rust and seedling resistance to stem rust with superior yield performance are, therefore, recommended as sources of resistance genes and candidates for deployment as varieties.
Key words: adult plant resistance, genotype-by-season interaction, grain yield, seedling resistance.
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