The evaluation of tan spot phenotype and the presence of necrotrophic effectors in the population of Pyrenophora tritici-repentis in Latvia

Tan spot is an economically important disease of wheat in Latvia, but there is still insufficient information about its causal agent’s Pyrenophora tritici-repentis diversity in Latvia. The aim of this study was to evaluate the disease phenotype in the field and the possible presence of necrotrophic effectors Ptr ToxA, Ptr ToxB and Ptr ToxC in the P. tritici-repentis population in Latvia. Typical differential wheat lines ‘Glenlea’, ‘6B662’, ‘6B365’ and ‘Salamouni’ were evaluated under the field conditions in 2023 in the central part of Latvia. The highest tan spot severity was observed during the flowering stage with no significant difference between wheat genotypes. During the experiment, the typical disease phenotypes corresponding to all three known effectors were noted. Additionally, typical tan spot symptoms were determined on the resistant cultivar ‘Salamouni’, confirming the presence of new, currently uncharacterised effectors that are not compatible with the existing race model. Future studies should focus on searching for new effectors and further characterising known necrotrophic effectors, as knowledge about P. tritici-repentis and wheat interaction is still incomplete.