P-562 - Evaluating marker-assisted selection for tan spot resistance in hard winter wheat

Abstract Text: Tan spot of wheat, caused by the necrotrophic fungal pathogen Pyrenophora tritici-repentis (Ptr), can significantly reduce yield, especially in reduced-tillage production systems. This fungus produces a host-selective toxin known as Ptr ToxA, which induces necrosis in wheat genotypes that carry the sensitivity gene Tsn1 located on chromosome arm 5BL. In Oklahoma, Ptr race 1 which produces ToxA, is the predominant race. This study aims to determine whether marker-assisted selection (MAS) using a Tsn1-linked marker can replace traditional phenotypic evaluations for tan spot resistance in the Oklahoma State University (OSU) wheat breeding program. A total of 229 OSU elite breeding lines and cultivars were selected and evaluated in the greenhouse for seedling responses to Ptr isolates collected from Oklahoma fields. Genotyping for Tsn1 is being conducted using a Kompetitive allele-specific PCR (KASP) marker, which is a high-throughput genotyping system. Phenotypic evaluations indicated that approximately half of the wheat collection exhibited moderate to high susceptibility to tan spot. The correspondence of Tsn1 genotype with phenotypic scores will be assessed to determine the reliability of MAS for large-scale selection in the OSU wheat breeding program. This study will provide insight into the effectiveness of marker-assisted elimination of Tsn1 for improving tan spot resistance in hard winter wheat breeding programs