Wheat (Triticum aetivum) 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, F 1 plants, F 2 populations, and F 3 and F 5 lines. The resistance to P.r. tritici pathotype TCB/TD in seedlings of Ciano 79 and Papago 86 was conferred by a single gene, Lr16. When present alone, Lr16 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 Lr16, 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
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R. P. Singh (1995) studied this question.