Purification and Characterization of Stagonospora nodorum Toxins and Mapping of Toxin Insensitivity

Stagonospora nodorum blotch disease caused by Phaeosphaeria nodorum is one of the most common diseases of wheat.  Host resistance is an important tool for managing losses due to this disease. Host-pathogen interactions in the wheat-P. nodorum pathosystem follow an inverse gene-for-gene interaction. The pathogen produces proteins that function as Host specific toxins (HSTs) by interacting with toxin sensitivity genes in the host. Several quantitative trait loci (QTL) have been identified for seedling reaction to P. nodorum in the Kenyon/86ISMN 2137 mapping population. This study focuses on the purification and characterization of individual HST, which will allow the mapping of corresponding toxin sensitivity genes in the host. A series of liquid chromatography techniques are used to purify targeted proteins. The purified proteins will be analyzed using mass spectrometry methods to further characterize or sequence the purified proteins. The map location of Snn3, which interacts with SnTox3, was mapped relative to SSR and SNP markers in the Kenyon/86ISMN 2137 population. Interestingly, the mapping population segregates for reaction to SnTox3 although no QTL for disease reaction was detected with conidia inoculations to seven P. nodorum isolates at the seedling stage. The map location of Tsn1, which interacts with SnToxA, was also added to the linkage map. The authors hope to map additional toxin sensitivity genes through this research and clone the corresponding HSTs from the pathogen. The long-term goal of the research is map-based cloning of toxin sensitivity genes in wheat and the development of high quality DNA markers for wheat breeding purposes.