Browsing by Author "Johansson, Annika"

Pyrenophora tritici-repentis (Ptr) and Parastagonospora nodorum (Pn) are necrotrophic fungal pathogens responsible for foliar diseases tan spot (TS) and stagonospora nodorum blotch (SNB) of wheat (Triticum aestivum L.), respectively. Both Ptr and Pn harbour necrotrophic effectors (NEs) to promote disease development. NEs elicit symptoms in the host in an inverse gene-for-gene manner, in which the recognition of NE by the host carrying a corresponding sensitivity allele leads to disease susceptibility. Ptr and Pn are prevalent in spring wheat fields in Finland, but Finnish spring wheat cultivars do not currently possess high level of resistance to either pathogen. The main objective of this study was to validate selection tools for TS and SNB resistance in Finnish spring wheat breeding program. A total of 150 spring wheat accessions were genotyped with six literature-derived Kompetitive Allele Specific PCR (KASP) markers associated with sensitivities to four NEs ToxA, ToxB, SnTox1 and SnTox3. A subset of 63 spring wheat accessions were further tested for their sensitivity to ToxA, SnTox1 and SnTox3, and for TS and SNB susceptibility at the seedling stage by artificial inoculation assays with fungal isolate mixtures. Field data on adult plant susceptibility was derived from official variety trials and from disease screenings carried out within a spring wheat breeding program at Boreal Plant Breeding Ltd. The association of KASP markers and NE sensitivities with seedling and adult plant susceptibility was tested, as well as the correlation of disease susceptibility at the seedling stage and in adult plants. ToxA sensitivity was found to have a significant role in TS susceptibility both at the seedling stage and in adult plants, suggesting that removing of ToxA sensitivity would result in spring wheat lines more resistant to TS. KASP marker for ToxA sensitivity was found to be tightly linked to TS susceptibility, thus serving an effective tool for TS resistance selection. ToxA and SnTox3 sensitivities were found to be important factors in SNB susceptibility at the seedling stage, and KASP markers for ToxA and SnTox3 sensitivities were associated with adult plant susceptibility. TS and SNB resistance were found to be complex traits, and further research is needed to better evaluate the role of NE sensitivities and other factors affecting disease susceptibility. This study provides the first insight into the role of NE sensitivities in TS and SNB susceptibility in Finnish spring wheat, and results obtained in this study are directly applicable for TS and SNB resistance breeding in Finnish spring wheat breeding programs.