Variation in virulence to wheat in Pyrenophora tritici-repentis population from Saskatchewan, Canada, from 2000 to 2002

Abstract

Tan spot, caused by Pyrenophora tritici-repentis, is an economically important disease of wheat worldwide. Isolates of P. tritici-repentis are presently classified into eight races on the basis of their virulence (ability to induce necrosis and (or) chlorosis) on a set of wheat differential cultivars. A total of 337 isolates of P. tritici-repentis from leaves of common wheat (Triticum aestivum), durum wheat (Triticum durum), einkorn wheat (Triticum monococcum), canary grass (Phalaris canariensis), and weedy grasses infected with tan spot were collected in wheat fields across Saskatchewan, Canada, from 2000 to 2002. Single-spore isolates were developed and tested on an expanded set of differential lines. Races 1, 2, 3, and 4 of P. tritici-repentis were identified in Saskatchewan. Race-2 isolates were the most prevalent on both common and durum wheat in all 3 years. Races 1, 2, and 4 were isolated from common wheat, and races 1, 2, and 3, from durum wheat. All race-3 isolates were detected from durum wheat, and while all race-4 isolates were from common wheat. Race 2 was isolated from canary grass, and races 1, 2, 3, and 4 were isolated from T. monococcum and wild grasses. To our best knowledge, this is the first report of the occurrence of P. tritici-repentis on canary grass and of race 3 on T. monococcum and wild grass.