Physiologic specialization ofPuccinia triticina, the causal agent of wheat leaf rust, in Canada in 2003

Abstract

Twenty-three virulence phenotypes, based on the infection types produced on 16 wheat differential lines, were identified from 97 isolates of Puccinia triticina, the causal agent of leaf rust on wheat, collected across Canada in 2003. Virulence phenotypes MCJJ, SBDJ, and TJBJ from Quebec were identified. Seven virulence phenotypes (MBDS, MBJS, TLGJ, MBPS, MBRJ, TBBJ, and TBRK) were detected among 13 isolates from Ontario. Twelve virulence phenotypes were detected among 73 isolates from Manitoba and Saskatchewan; the most prevalent were TBBJ, MBDS, and KBBJ. There was a decline in the frequency of virulence to Lr16 in Manitoba and Saskatchewan from 33.3% in 2002 to 4.1% in 2003. Six virulence phenotypes (BBBN, LBDS, MBBJ, MBDS, TBDJ, and TJBJ) were identified among seven isolates from Alberta. Among 29 isolates, representative of most virulence phenotypes tested on additional differentials, 13, 25, 27, 27, 17, and 14 isolates were virulent to seedling plants with Lr2b, Lr3bg, Lr14b, Lr20, Lr23, and Lr28, respectively. No isolates were virulent to Lr19, Lr21, Lr25, Lr29, or Lr32, while all isolates were virulent to Lr15. There were 24, 24, 1, 22, and 28 isolates virulent to adult plants with Lr12, Lr13, Lr35, Lr37, and to 'Thatcher', respectively, but none were virulent to Lr22a or Lr34.