Identification of QTL in Spring Wheat Associated with Resistance to a Novel Isolate of Pyrenophora tritici-repentis

Tan spot, caused by Pyrenophora triticirepentis, is an important disease of wheat (Triticum aestivum L.) worldwide. Pathogenic races of P. tritici-repentis have been identified on the basis of their ability to induce tan necrosis and/or chlorosis symptoms on differential wheat genotypes. A group of isolates of P. triticirepentis collected from Arkansas 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. An association mapping approach and 832 polymorphic diversity array technology markers were used to identify quantitative trait loci (QTL) associated with resistance to the isolate AR CrossB10. Two models (QK(1) and QK(2)) with the least mean square difference 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 genes also are clustered around a few of the significant markers and will be useful for wheat breeding programs and for search of candidate genes.