|Bonman, John - Mike|
|Del Rio, Luis|
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2011
Publication Date: 7/9/2011
Citation: Gurung, S., Mamid, S., Bonman, J.M., Jackson, E.W., Del Rio, L.E., Acevedo, M., Adhikari, T.B. 2011. Identification of novel genomic regions associated with resistance to Pyrenophora tritici-repentis races 1 and 5 in spring wheat landraces using association analysis. Theoretical and Applied Genetics. 123:1029-1041. Interpretive Summary: Tan spot is a disease of wheat that is increasing in importance worldwide. It is favored by no-till cropping systems. Planting resistant wheat cultivars is the most economically feasible means of managing tan spot. To help plant breeders develop resistant cultivars, new sources of resistance are needed. We tested spring landrace cultivars from the National Small Grains collection for resistance to tan spot and then use a method known as ‘association mapping’ to determine the location of resistance within the wheat genome. Using this method, we verified some previously identified loci for resistance and discovered other loci that may be novel. These loci can now be studied further and eventually used by wheat breeding programs to develop resistant cultivars useful for tan spot management.
Technical Abstract: Tan spot, caused by Pyrenophora tritici-repentis, is a major foliar disease of wheat worldwide. Host plant resistance is the best strategy to manage this disease. Traditionally, bi-parental mapping populations have been used to identify and map quantitative trait loci (QTL) affecting tan spot resistance in wheat. Association mapping (AM) could be an alternative approach to identify QTL based on linkage disequilibrium (LD) within a diverse germplasm set. In this study, we assessed tan spot resistance (races 1 and 5) in 567 spring wheat landraces from the USDA-ARS National Small Grains Collection (NSGC). Using 832 Diversity Array Technology (DArT) markers, QTL for resistance to P. tritici-repentis races 1 and 5 were identified. A linear model with principal components suggests that at least seven and three DArT markers were significantly associated with resistance to tan spot races 1 and 5, respectively. The DArT markers associated with resistance to race 1 were detected on chromosomes 1D, 2A, 2B, 2D, 4A, 5B, and 7D and explained 1.3 to 3.1% of the phenotypic variance, while markers associated with resistance to race 5 were distributed on 2D, 6A and 7D, and explained 2.2 to 5.9% of the phenotypic variance. The genetic regions identified in this study also correspond to previously identified loci responsible for resistance P. tritici-repentis, offering validation for our association mapping approach. Some DArT markers associated with resistance to race 1 also were localized in the same regions of wheat chromosomes where QTL for resistance to yellow rust, leaf rust and powdery mildew, have been mapped previously. This study demonstrates that AM can be useful approach to identify and map novel resistance to P. tritici-repentis that can be utilized in wheat breeding programs via marker-assisted selection (MAS).