Alberta regional meeting, 2022 / Réunion régionale de l’Alberta, 2022

Pyrenophora tritici-repentis (tan spot) is a complex foliar pathogen that primarily infects hexaploid (bread) and tetraploid (durum) wheat, as well as a variety of wild grass species. Eight races of P. tritici-repentis have been described worldwide, based on their virulence patterns on a host differential set. The virulence of these races reflects their capacity to produce three known necrotrophic effectors (NE), either alone or in various combinations. Recently, ‘atypical’ isolates of P. tritici-repentis , which induce the necrosis typical of some of these races but lack the corresponding NE, were identified from durum wheat in North Africa (Tunisia), a secondary centre of diversity of this crop. The aim of this study was to char-acterize additional collections of P. tritici-repentis from Tunisia, in order to determine their virulence profiles and assist in the identification of novel races and NEs. Preliminary characterization of 53 isolates on the standard differential set indicated that 16.6% were classified as races 3 and 8, while 50% were race 5. In addition, 16.6% of the isolates appeared to induce atypical responses, meaning that the host response to inoculation did not seem to fit the standard reactions to the eight known races. Additional testing is underway to confirm these reactions, and all isolates will be assessed for the presence or absence of the known NE-encoding genes. An improved knowledge of the virulence of P. tritici-repentis , including the occurrence of novel races and NEs, will be important for the sustainable management