|Kolmer, James - Jim|
Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/2/2006
Publication Date: 4/1/2007
Citation: Kolmer, J.A., Oelke, L.M. Genetics of Leaf Rust Resistance in the Spring Wheat Cultivars Ivan and Knudson. Canadian Journal of Plant Pathology. 28:223-229. Interpretive Summary: Leaf rust is a disease of wheat caused by the fungus Puccinia triticina. Hard red spring wheat cultivars grown in Minnesota and the Dakotas are attacked every year by this fungus. Wheat cultivars can be very resistant to the leaf rust fungus if they have combinations of certain genes that give resistance to the fungus. The objective of this study was to determine which leaf rust resistance genes are present in the wheat cultivars Knudson and Ivan. Knudson was determined to have the resistance genes Lr3, Lr10, Lr13, Lr16, Lr23, and Lr34. Most of the resistance in Knudson would be due to the combination of genes Lr23, Lr16, and Lr34. The resistance genes Lr16 and Lr24 were identified in Ivan. Gene Lr34 has conditioned durable resistance to leaf rust in wheat cultivars around the world. Since Ivan lacks Lr34, this cultivar may become susceptible to leaf rust if leaf rust races with virulence to genes Lr16 and Lr24 increase.
Technical Abstract: Leaf rust, caused by Puccinia triticina, is a common and widespread disease of wheat in North America and world-wide. Stable genetic resistance to leaf rust in wheat has been difficult to achieve since the leaf rust pathogen is highly variable for virulence to specific leaf rust resistance genes in wheat. Ivan and Knudson are hard red spring wheat cultivars recently released by AgriPro that are highly resistant to leaf rust. The objective of this study was to determine the identity of leaf rust resistance genes present in both cultivars. Ivan and Knudson were crossed with the leaf rust susceptible cultivar Thatcher; the F1 plants were backcrossed to Thatcher; and the BCF1 plants (approximately 80 from each cross) were selfed to develop BCF2 families. The BCF2 families were tested as seedlings with different isolates of P. triticina to determine the number and identity of leaf rust resistance genes that segregated. Selected lines derived from BCF2 plants were tested with different leaf rust isolates to confirm the identity of the leaf rust resistance genes that segregated in the BCF2 families. Selected BCF2 families were also tested as adult plants in greenhouse tests and field plots to identify adult plant leaf rust resistance genes. Ivan was determined to have genes Lr24 and Lr16; Knudson was determined to have Lr3, Lr10, Lr13, Lr16, Lr23, and Lr34. Ivan has been highly resistant because of the rarity of leaf rust isolates with virulence to Lr16 and Lr24, while the interactions between genes Lr16, Lr23, and Lr34 account for the resistance in Knudson.