Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2007
Publication Date: 8/21/2007
Citation: Vanegas, C.D., G., Kolmer, J.A., Garvin, D.F. 2008. Genetics of stem rust resistance in the spring wheat cultivar thatcher and the enhancement of stem rust resistance by Lr34. Euphytica. 159(3):391-401. Interpretive Summary: Thatcher is a spring wheat that was developed in Minnesota in the 1930’s. Many of the current spring wheats currently have Thatcher in their parentage. Thatcher has resistance to stem rust, caused by Puccinia graminis that is best expressed in the adult plant stage in field plots that have been inoculated with stem rust. The gene Lr34 which gives resistance to the leaf rust pathogen, Puccinia triticina, when present in Thatcher allows the expression of additional stem rust resistance genes in Thatcher. In seedling plants and in adult plants the presence of Lr34 in lines derived from Thatcher had superior stem rust resistance compared to lines without Lr34. A region on chromosome 2BL in wheat was associated with adult plant stem rust resistance in Thatcher. The additional Thatcher resistance that is expressed in the presence of Lr34 can be used to develop wheat cultivars with high levels of stem rust resistance.
Technical Abstract: Three recombinant inbred line populations from the crosses RL6071/Thatcher, RL6071/RL6058 (Thatcher Lr34), and Thatcher/RL6058, were used to study the genetics of stem rust resistance in Thatcher. Segregation of stem rust resistance in each population was used to determine the number of genes conferring resistance, as well as the effect of the leaf rust resistance gene Lr34 on stem rust resistance. The relationship between seedling and adult resistance was also examined, and an attempt was made to identify microsatellite markers linked to adult plant resistance genes. In field plot tests of adult plants, at least three additive adult resistance genes segregated in the RL6071/RL6058 population, while two resistance genes segregated in the RL6071/Thatcher population. The presence of the gene Lr34 permitted the expression of additional stem rust resistance in Thatcher-derived lines both at the seedling and adult plant stages. Seedling resistance to races TPMK and RKQQ was significantly associated with adult plant resistance, while seedling resistance to races QCCD and QCCB may have made a minor contribution to adult resistance. The seedling genes Sr16 and Sr12 may have contributed to adult resistance. A molecular marker linked to adult resistance was identified on chromosome 2BL.