Physiological specialization of <i>Puccinia triticina</i>, the causal agent of wheat leaf rust, in Canada in 2014

Abstract

Wheat leaves infected with Puccinia triticina, the causal agent of wheat leaf rust, were collected from across Canada in 2014. From these leaves, 102 single-pustule isolates were recovered and tested for virulence on 16 standard differential wheat lines, with 28 unique virulence phenotypes found. The most common were TBDG (16.7%), TBBG (13.7%), MLPS and TNBG (both at 7.8%). Most isolates (95) originated from Manitoba and Saskatchewan, and the most common phenotypes found in this region were TBDG (17.9%), TBBG (14.7%), MLPS and TNBG (both at 8.4%). From Ontario, six virulence phenotypes were found from seven isolates: TCGJ (two isolates), MBDS, MCQG, MFPS, MGBS and TBGS (one isolate each). Frequencies of virulence in 2014 increased for Lr2a, Lr2c, Lr26 and Lr10 when compared with 2013, while there were decreases in virulence to Lr9, Lr24, Lr3ka, Lr30, Lr14a, Lr21 and LrCen. When 30 isolates, representing most of the unique virulence phenotypes, were tested on adult plants nearly all were virulent to the adult plant resistance genes Lr12, Lr13 and Lr37, most were avirulent to Lr35, and all were avirulent to Lr22a. When this subset of isolates was inoculated onto additional seedling differentials, most were virulent to Lr15 and Lr14b and avirulent to Lr25 and Lr29, and all isolates were avirulent to Lr19, Lr32 and Lr52. There were intermediate levels of virulence on Lr3bg, Lr20, Lr23 and Lr28.