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Genetics

Inheritance of the Leaf Rust Resistance of Four Triticale Cultivars. Jeffrey Wilson, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, Present address: USDA-ARS, Coastal Plain Experiment Station, Tifton, GA 31793-0748; Gregory Shaner, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 79:731-736. Accepted for publication 2 March 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-731.

The inheritance of resistance to culture 7434-1-1T of Puccinia recondita f. sp. tritici was examined in four triticales that were selected as potential sources of resistance genes for wheat. The resistant triticales were each crossed to the susceptible triticale PI 429007. The parents and the F₁, F₂, and F₃ progeny were evaluated for segregation of infection type (IT) to determine the number and dominance of genes for resistant IT that each cultivar possesses. The resistant cultivars were crossed to each other and the F₂ and F₃ progeny were evaluated to examine the relationships of the resistance genes. The F₃ progeny with susceptible IT derived from the resistant × susceptible crosses were evaluated for the presence of genes for long latent period, an important component of slow-rusting resistance. PI 429120 possesses two independent, incompletely dominant genes that together confer a 0;n IT in the adult plant. PI 429155 possesses one incompletely dominant gene that confers a 12c IT. PI 429121 expresses a 0;1n IT, and PI 429215 expresses a 0;n IT. Both of these cultivars possess one incompletely dominant gene with a major effect and an additional minor gene that confers a nearly susceptible, mesothetic IT. The minor-effect gene in PI 429121 is recessive, whereas that in PI 429215 is partially dominant. The genes in PI 429120 are independent of those in the other cultivars. PI 429215 has a gene in common with PI 429121, and this major-effect gene is linked approximately nine map units from the gene in PI 429155. The four cultivars each possess an undetermined number of partially recessive genes for long latent period in addition to their genes for resistant IT. These triticales may be useful both as sources of leaf rust resistance for wheat and as examples for the directed use of genes for low-IT and slow-rusting resistances.