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Inheritance of Seedling and Adult Plant Resistance to Leaf Rust in Wheat Cultivars Ciano 79 and Papago 86. R. P. SINGH, International Maize and Wheat Improvement Center (CIMMYT), Lisboa 27, Apdo. Postal 6-641, 06600, Mexico. D.F. Mexico, and J. HUERTA-ESPINO, SARH, INIFAP, CIANO, Km. 12. Carret. Norman Borlaug, Apdo. Postal 515, 8500, Cd. Obregon, Son., Mexico. Plant Dis. 79:35-38. Accepted for publication 13 September 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0035.

Wheat (Triticum aestivum) cultivars Ciano 79 and Papago 86 have maintained high levels of resistance to leaf rust, caused by Puccinia recondita f. sp. tritici, since their release during 1979 and 1986, respectively, in leaf rust-prone northwestern Mexico. Because inheritance of leaf rust resistance for these cultivars is unknown, Ciano 79 and Papago 86 were intercrossed, crossed with the susceptible cultivar Sonora 64, and crossed with the adult plant resistant cultivar Frontana to evaluate the resistance relationship. Inheritance studies were conducted in seedling and/or adult plant growth stages using the parents, F1 plants, F2 populations, and F3 and F5 lines. The resistance to P. r. tritici pathotype TCB/TD in seedlings of Ciano 79 and Papago 86 was conferred by a single gene, Lrl6. When present alone, Lrl6 confers only moderate resistance in adult plants to the same pathotype. The adult plant resistances of both cultivars were based on the additive interaction between gene Lr16 and a minimum of two other slow-rusting genes. Besides Lrl6, one of the two slow-rusting genes was also common in Ciano 79 and Papago 86. The adult plant resistance genes in these cultivars differed from the resistance genes in Frontana.