Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2010
Publication Date: 5/1/2010
Citation: Kolmer, J.A. 2010. Genetics of Leaf Rust Resistance in the Soft Red Winter Wheat Cultivars Coker 9663 and Pioneer 26R61. Plant Disease. 94:628-632.
Interpretive Summary: Leaf rust, caused by the fungus Puccinia triticina is the most common disease of wheat in the United States. The objectives of this research was to identify the leaf rust resistance genes in the soft red winter wheats Coker 9663 and Pioneer 26R61, which have been widely grown in the southeastern states. Coker 9663 was determined to have genes Lr9, Lr10, Lr14a, and additional resistance that was not identfied. Pioneer 26R61 was determined to have Lr13, Lr14b, and Lr26. Genes Lr9 and Lr26 are very common in the soft red winter cultivars and are important for leaf rust resistance in these cultivars. Currently few races of leaf rust with virulence to Lr9 are present in the United States, however many races with virulence to Lr26 are currently found. Cultivars with Lr9 should have some leaf rust resistance, while cultivars with Lr26 would likely be more susceptible. Identification of leaf rust genes present in wheat cultivars allows wheat breeders and plant pathologists to develop wheat cultivars with long lasting resistanc to leaf rust.
Technical Abstract: Leaf rust, caused by the fungus Puccinia triticina, is an important disease of soft red winter wheat cultivars that are grown in the southern and eastern United States. The objectives of this study were to identify the leaf rust resistance genes in two soft red winter wheat cultivars, Coker 9663 and Pioneer 26R61 that have been widely grown and were initially highly resistant to leaf rust. Both cultivars were crossed with the leaf rust susceptible spring wheat cultivar Thatcher and the F1 plants were backcrossed to Thatcher to obtain backcross F2 families. In seedlings, the Thatcher*2/Coker 9663 F2 families segregated for three independent seedling resistance genes when tested with different leaf rust isolates. The leaf rust infection types of selected backcross F3 lines when tested with different leaf rust isolates indicated that seedling resistance genes Lr9, Lr10, and Lr14a were present. In field plot tests, backcross F4 lines that were seedling susceptible had some adult plant resistance to leaf rust. Seedlings of the Thatcher*2/Pioneer 26R61 F2 families segregated for two independent resistance genes. Infection types of selected backcross F3 lines indicated the presence of Lr14b and Lr26. The adult plant gene Lr13 was determined to be present in selected backcross F4 lines that were tested with different leaf rust isolates in greenhouse tests.