|Bonman, John - Mike|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2012
Publication Date: N/A
Citation: N/A Interpretive Summary: Tan spot is an important disease of wheat worldwide. New races of the tan spot pathogen develop over time and it is necessary to screen wheat germplasm for sources of resistance to both new and existing races of the pathogen. It is also valuable to better understand genetic basis of tan spot resistance in wheat. We used a technique known as ‘association mapping’ to locate resistance to a novel isolate of the tan spot pathogen from Arkansas among wheat accessions from the National Small Grains Collection. Molecular markers associated with the resistance may eventually prove useful in efforts to breed new tan spot resistant wheat cultivars.
Technical Abstract: Tan spot, caused by Pyrenophora tritici-repentis, is an important disease of wheat worldwide. Pathogenic races of P. tritici-repentis have been identified based on their ability to induce tan necrosis and/or chlorosis symptoms on differential wheat genotypes. Race 1 causes necrosis and extensive chlorosis on Glenlea and 6B365, respectively. Similar disease reactions were found on these differential wheat genotypes when inoculated with a group of isolates of P. tritici-repentis collected from Arkansas. These isolates did not fit into the current race classification system because they lack the ToxA gene. In this study, 535 spring wheat accessions were inoculated with a representative novel isolate (AR CrossB10) of P. tritici-repentis.from Arkansas. Association mapping (AM) approach and 832 polymorphic Diversity Array Technology (DArT) markers were employed to identify quantitative trait loci (QTL) associated with resistance to the isolate AR CrossB10. Two best models (QK1 and QK2) with the least mean square difference (MSD) were selected among nine linear regression models tested, and 11 QTL involved in resistance to AR CrossB10 were identified, which are located on chromosomes 1A, 1D, 2B, 2D, 6A and 7A. The results suggest that multiple disease resistance (MDR) genes also are clustered around few of the significant markers and will be useful for wheat breeding programs and for search of candidate genes.