Physiologic specialization of wheat leaf rust (<i>Puccinia triticina</i>) in Canada in 2002

Abstract

Abstract Forty virulence phenotypes of Puccinia triticina were identified from 295 isolates collected across Canada in 2002 on 16 Triticum aestivum ‘Thatcher’ near-isogenic lines. The most frequent virulence phenotypes across Canada were MBDS (30.2%), TGBJ (22.0%), TBBJ (9.5%), and TBDS (7.8%). There were 10 virulence phenotypes identified among 24 isolates from Quebec; MBRK (29.2%), TBRJ (16.7%), MBRJ (12.5%), and TLGJ (12.5%) were the most frequent. Ten virulence phenotypes were identified among 22 isolates from Ontario, with PCLR and PCMR (both 22.7%) being the most frequent. There were 25 virulence phenotypes identified from 234 isolates collected in Manitoba and southeastern Saskatchewan; MBDS (32.9%), TGBJ (27.4%), and TBBJ (11.5%) were the most frequent. The frequency of virulence to Lr16 declined in Manitoba and Saskatchewan from 74.1% in 2001 to 33.3% in 2002 while the frequency of virulence to Lr17 increased from 23.8% in 2001 to 53.4% in 2002. Five virulence phenotypes were identified from 15 isolates collected in Alberta. These were MBDS (11 isolates), TBBJ, TBDS, TCRK, and TGBJ (all one isolate each). A subsample representative of the field isolates collected in 2002 was tested for virulence on adult plants. All 71 isolates tested were avirulent to adult-plant resistance genes Lr22a, Lr34, and Lr3, and to seedling genes Lr21 and Lr32 which are best expressed in adult plants. The isolates varied for virulence to adult-plant resistance genes Lr12 and Lr37, and only one isolate was avirulent to Lr13. Keywords: racesbrown rustPuccinia recondita