|Kolmer, James - Jim|
Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/3/2005
Publication Date: 6/10/2005
Citation: Oelke, L.M., Kolmer, J.A. 2005. Genetics of leaf rust resistance in the spring wheat cultivars Alsen and Norm. Phytopathology. 95:773-778. 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 Alsen and Norm. Alsen is widely grown since it has good leaf rust resistance and also has some resistance to the disease Fusarium head blight. Alsen was determined to have the resistance genes Lr2a, Lr10, Lr13, Lr23, and Lr34. Most of the resistance in Alsen would be due to the combination of genes Lr13, Lr13, and Lr34. Norm has been highly resistant to leaf rust since release in the mid 1990s. Genes Lr1, Lr10, Lr13, Lr16, Lr23, and Lr34 were determined to be in Norm. The resistance in Norm would be mostly due to the combination of genes Lr13, Lr16, Lr23, and Lr34. Gene Lr34 has conditioned durable leaf rust resistance in many wheats found throughout the world. Alsen is widely grown in Minnesota and North Dakota. Because Alsen combines good leaf rust resistance with Fusarium head blight resistance, it could be used as a parent in breeding programs to produce high-yielding lines with good disease resistance. The combination of resistance genes in Norm gives extremely good resistance to leaf rust. Norm can be used as a parent in wheat breeding programs to improve the overall level of leaf rust resistance.
Technical Abstract: Alsen is a recently released spring wheat that has been widely grown in the U.S. since it has resistance to Fusarium head blight and leaf rust caused by Puccinia triticina. Norm is a high yielding wheat that has been very resistant to leaf rust since being released. Alsen and Norm were genetically examined to determine the number and identity of the leaf rust resistance genes present in both wheats. The two cultivars were crossed with the leaf rust susceptible cultivar Thatcher and the F1 plants were backcrossed to Thatcher. Eighty one and 73 BCF1of Thatcher x Alsen, and Thatcher x Norm respectively, were selfed to obtain BCF2 families. The BCF2 families were tested as seedlings with different isolates of P. triticina that differed for virulence to specific leaf rust resistance genes. The BCF2 families that lacked seedling resistance were also tested as adult plants in greenhouse tests and in a field rust nursery plot. Segregation of BCF2 families indicated that Alsen had the seedling genes Lr2a, Lr10, and Lr23, and the adult plant genes Lr13 and Lr34. Norm was determined to have the seedling genes Lr1, Lr10, Lr16, and Lr23, and the adult plant genes Lr13 and Lr34. The characterization of Lr23 in the segregating populations was complicated by the presence of a suppressor gene in Thatcher and the high temperature sensitivity of resistance expression for this gene. The effective leaf rust resistance in Alsen is due to the interaction of Lr23 with Lr34, and the effective leaf rust resistance in Norm is due to the interaction of Lr16, and Lr23, with Lr34.