Leaf rust resistance in selected late maturity, common wheat cultivars from Uruguay

Leaf rust (caused by Puccinia triticina) is one of the most important diseases of wheat in Uruguay, and breeding for resistance to this disease is a priority for the INIA wheat program. Knowledge of the effective resistance genes present in the germplasm is relevant when selecting for effective and more durable resistance. The leaf rust resistance present in six adapted wheat cultivars that are parents of many advanced lines was studied. Races of P. triticina with different virulence combinations were used to determine which seedling resistance genes might be present in the six cultivars and/or derived lines. Genetic analysis of seedling and adult plant resistance (APR) was conducted on BC₁F₂ and F₃ generations from crosses of four cultivars with the susceptible cultivar Thatcher. The presence of APR genes Lr13 and Lr34 was confirmed with crosses of the four cultivars and Thatcher lines with these genes. A genetic marker associated with Lr34 was used to postulate the presence of this gene in all cultivars. The cultivars and resistance genes postulated to be present were: Estanzuela Calandria Lr3bg, Lr16 and Lr24; Estanzuela Federal Lr10; Estanzuela Halcón Lr10, Lr14a, and Lr16; INIA Tijereta and INIA Garza Lr16, Lr24 and Lr34; and INIA Torcaza Lr10 and Lr24. Only Lr16 and Lr34 remain effective to the predominant pathotypes. Additional ineffective seedling resistance that could not be identified was present in E. Federal, I. Tijereta and I. Torcaza. Unknown APR gene(s) could be present in E. Calandria and E. Federal.