Genetic Analysis of Resistance to Leaf Rust in Nine Durum Wheats. R. P. Singh, International Maize and Wheat Improvement Center (CIMMYT), Lisboa 27, Apdo. Postal 6-641, 06600, Mexico, D.F., Mexico. E. Bechere, and O. Abdalla. International Maize and Wheat Improvement Center (CIMMYT), Lisboa 27, Apdo. Postal 6-641, 06600, Mexico, D.F., Mexico. Plant Dis. 77:460-463. Accepted for publication 7 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0460.

High-yielding durum wheat (Triticum turgidum) cultivars, derived from the CIMMYT (International Maize and Wheat Improvement Center) germ plasm, are grown on approximately 40% of the global durum wheat area. Because of the lack of information on their genes for resistance to leaf rust, crosses in a diallel arrangement (without reciprocals) were made among nine resistant CIMMYT-derived durums and the accession DW7276, which is susceptible to Mexican Puccinia recondita f. sp. tritici pathotype BBB/BN. Mexican durums were also crossed with the adult-plant resistant land race cultivar Iumillo. Inheritance of resistance was investigated in seedlings and/or adult plants of F₁ hybrids, F₂ populations, and F₃ lines. A common, partially dominant gene confers seedling resistance in Altar 84, Carcomun, Morus, and Totanus. This gene alone does not confer an acceptable level of adult-plant resistance; however, it interacts in an additive manner with two additional partially effective adult-plant genes. Two additive genes also confer adult-plant resistance to Mexicali 75, Yavaros 79, Diver, Kingfisher, and Somorguho. At least one adult-plant gene is common in each resistant parent. However, transgressive segregation in the F₂ and F₃ generations for reduced or increased adult-plant leaf rust severity indicates genetic diversity. CIMMYT durums and worldwide-resistant Iumillo carry common adult-plant resistance, which could be of a durable nature.