A note on the impact of CYP51 alterations and their combination in the wheat pathogen Zymoseptoria tritici on sensitivity to the azole fungicides epoxiconazole and metconazole

Septoria tritici blotch caused by the fungal pathogen Zymoseptoria tritici is the most economically damaging disease of winter wheat in Ireland. As azoles have been intensively used, Z. tritici has developed different means of resisting their toxic effects with multiple alterations now reported in individual strains. Using previously characterised Irish collections of Z. tritici, the relationships between these different alterations have been examined using conditional inference trees and random forest. The results from this study highlight the importance of specific alterations I381V and S524T, with both contributing most to the reductions in epoxiconazole (EPZ) and metconazole (MTZ) sensitivity. As the azole class of fungicides is an extensive and diverse group, it is possible these alterations do not impact other azoles in a similar manner. Further analysis of these and contemporary collections to additional azoles, including mefentrifluconazole, which continues to provide good field control of Z. tritici, is warranted.