Resistance to Stripe Rust in Five Durum Wheat Cultivars

Durum wheat (Triticum turgidum) cultivars developed by the International Maize and Wheat Improvement Center (CIMMYT) are currently grown on more than 8 million hectares worldwide. Because of the lack of information on the genetic basis of resistance to stripe rust (caused by Puccinia striiformis), crosses in a diallel arrangement (without reciprocals) were made among five worldwide resistant cultivars and the susceptible cultivar Local Red. Inheritance of resistance was investigated in seedling and adult plant growth stages of F₂ populations, and F₃lines. The low seedling infection type of each resistant cultivar, namely Kroub 76, Chonta Inia, Sna 3, Syros, and Arena, was based on the additive action of the same two genes. Each of these genes conferred intermediate infection types when present alone. The field resistance of the cultivars was based on the additive action of the two genes identified in the seedlings and one additional, partially effective adult resistance gene. Segregation for plants with stripe rust severities higher than that of the parents in intercrosses of resistant cultivars indicated that some genetic diversity exists for adult genes. The resistance of these cultivars may prove to be long-lasting, since it results from the combined action of at least three genes.