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Inheritance of Stem Rust Resistance in Triticum aestivum, 'C. I. 14115', a Powdery Mildew Differential. F. J. Gough, Plant Pathologist, USDA, ARS, College Station Texas 77843; O. G. Merkle, Agronomist, USDA, ARS, College Station Texas 77843. Phytopathology 64:1105-1108. Accepted for publication 8 March 1974. DOI: 10.1094/Phyto-64-1105.

Inheritance of seedling resistance to stem rust was studied in the F₃ and F₄ of Triticum aestivum 'C. I. 14115' × susceptible 'Little Club'. Resistance to culture 111-SS2 (physiologic race 111) of Puccinia graminis f. sp. tritici was conditioned by two independent dominant genes and to culture 69-21-399 (physiologic race 151) by a single dominant gene. The gene for resistance to culture 69-21-399 was associated with one of the genes for resistance to culture 111-SS2. Neither of the three genes was associated with the gene for mildew resistance, Pm1. The presence of the gene, Sr15, for resistance to stem rust was demonstrated by I. A. Watson in several F₃ and F₄ families by testing them with certain cultures indigenous to Australia. Tests conducted by A. P. Roelfs with cultures of physiologic races 17A, 32, and 177 (which collectively had genes for avirulence corresponding to genes for resistance, Sr5, Sr6, Sr7b, Sr8, Sr9a, Sr9b, Sr9d, Sr10, Sr11, and Sr14) failed to indicate additional genes for resistance in 40 F₅ families (from 16 F₂ families) homozygous for susceptibility to cultures 111-SS2 and 69-21-399.