Submitted to: Eastern Wheat Workers and Southern Small Grain Workers Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: April 6, 2009
Publication Date: May 20, 2009
Citation: Kolmer, J.A., Long, D.L. 2009. Leaf rust resistance in soft red winter wheats and virulence in Puccinia triticina. Eastern Wheat Workers and Southern Small Grain Workers Proceedings. pp. 1-3. Technical Abstract: Leaf rust caused by Puccinia triticina is a common disease of soft red winter wheat in the southeastern and eastern U.S. Seedling infection type studies of soft red winter wheat cultivars indicated that leaf rust resistance genes Lr11, Lr14a, and Lr26 are very common in this wheat class. Genes Lr1, Lr2a, Lr9, Lr14a, Lr18, and Lr24 were also postulated to be present in these cultivars at lower frequency. Leaf rust races with virulence to these genes have been found in the soft red winter wheat area, thus none of these genes condition resistance to all leaf rust races. Genetic analysis of leaf rust resistance in selected soft red winter wheat cultivars indicated that Pioneer 26R61 has genes Lr13, Lr14b, and Lr26; Coker 9663 has genes Lr9, Lr10, Lr14a, and adult plant resistance; and Caldwell has Lr12, Lr14a, and an adult plant resistance gene. Thatcher backcross lines with adult plant resistance derived from Coker 9663 and Caldwell had intermediate levels of resistance in inoculated plots at St. Paul Minnesota. Testing of soft red winter wheat cultivars with the Lr34 linked marker csLV34 indicated that none of the cultivars had the marker allele associated with Lr34. European winter wheat and U.S. hard red winter wheat cultivars are possible sources of Lr34 for this wheat class. From 2004-2007 P. triticina isolates with virulence to Lr9, Lr11 and Lr18 declined in frequency in the soft red winter wheat region, due to an increase of isolates with virulence to Lr17, Lr24 and Lr26. In 2007 the most common leaf rust races in the soft red winter wheat region were MFPSC (Lr17, Lr24, Lr26 virulence), TCRKG (Lr11, Lr26, Lr18 virulence), TFBJG (Lr24, Lr26 virulence), and TDBJG (Lr24 virulence). Race MFPSC and most other races with Lr17 virulence have distinct SSR (simple sequence repeat) molecular genotypes compared to races that are avirulent to Lr17. Races with Lr17 virulence were likely introduced to the southern Great Plains in the mid 1990s and were selected by the hard red winter wheat Jagger. These races are now widespread throughout the U.S.