Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/2/2002
Publication Date: 7/1/2003
Citation: KOLMER, J.A. LEAF RUST RESISTANCE IN SOFT RED WINTER WHEAT. CROP SCIENCE. 2003. v. 43. p. 1266-1274. Interpretive Summary: Wheat grown in the United States is attacked by a fungus that is called leaf rust. Every year leaf rust can be found on wheat almost wherever wheat is grown in the United States. In the southern United States, soft red winter wheat is commonly grown. One way to reduce the attack of leaf rust on wheat is to develop wheats that have resistance to the leaf rust fungus. For this research, the genes in 28 wheat cultivars and 24 wheat breeding lines that give resistance to the leaf rust fungus were characterized and identified in greenhouse tests. Different collections of the fungus that are genetically different were used to infect the wheat cultivars and breeding lines. Wheat plants that had different resistance genes gave different levels of infection to the different leaf rust isolates. The genes that were identified in the wheat cultivars and lines were leaf rust resistance gene 1 (Lr1), Lr2a, Lr9, Lr10, Lr11, Lr18, and Lr26. A very important leaf rust resistance gene, Lr34, may also be present in many of the wheat cultivars and breeding lines. This research will help wheat breeders and plant pathologists develop new wheat cultivars that have good resistance to the leaf rust fungus.
Technical Abstract: Leaf rust, caused by the fungus Puccinia triticina, is a major disease nearly wherever wheat is grown in the United States. Soft red winter wheat cultivars with varying degrees of leaf rust resistance are grown throughout the southern United States. The objective of this study was to characterize the seedling leaf rust resistance present in a group of 28 soft red winter wheat cultivars and 24 breeding lines. The wheat cultivars and lines were tested for seedling resistance with a diverse group of 16 P. triticina isolates. Leaf rust infection types produced on the cultivars and lines by the leaf rust isolates were compared with the infection types produced on a standard set of Thatcher near-isogenic lines that differed for single leaf rust resistance genes. Isolates that produced low infection type to seedling resistance genes in the Thatcher near-isogenic lines also produced low infection on cultivars and lines that had the same seedling resistance genes. Seedling resistance genes Lr1, Lr2a, Lr9, Lr10, Lr11, Lr18, and Lr26, were postulated to be present in the soft red winter wheat cultivars and lines. Adult plant leaf rust resistance for the cultivars and lines was assessed in field plots at two locations in North Carolina in 2000. Wheat cultivars postulated or genetically determined to have the adult plant resistance genes Lr12 and Lr34 had effective leaf rust resistance in the field plots. The soft red winter wheat cultivars and lines that had seedling resistance genes Lr2a, Lr9, and Lr26, combined with adult plant resistance, were highly resistant to leaf rust. Cultivars and breeding lines that had seedling resistance genes Lr1, Lr10, Lr11, and Lr18, combined with adult plant resistance had moderate to low levels of leaf rust resistance.