Physiological specialization of<i>Puccinia triticina</i>in Canada in 2007

Abstract

Puccinia triticina, the causal agent of wheat leaf rust, is a damaging and rapidly changing pathogen in Canada and throughout the world. To determine the virulence present in this pathogen population, 381 single-pustule derived P. triticina isolates were made from infected leaf collections from across Canada in 2007. Five virulence phenotypes were identified from 11 isolates collected in British Columbia and Alberta, the most common of these was MBDS. There were 14 unique virulence phenotypes among 323 isolates from Manitoba and eastern Saskatchewan. The most common of these were TDBG (61.0%), TDBJ (15.2%), MDPS (5.3%), and MDLS (5.3%). Nine virulence phenotypes were identified among 33 isolates from Ontario, with MLDS (36.4%), TDBG (21.2%), and TDBJ (15.2%) being the most common. Five virulence phenotypes were identified among 10 isolates from Quebec. The most common of these were TDBJ and TDBG (three isolates each) and MFDS (two isolates). Each of the four isolates from Prince Edward Island represented a different virulence phenotype (MCNS, MFDS, MHNQ and MHNS). These were all unique to Prince Edward Island, except for MFDS. The frequencies of virulence to Lr2a, Lr2c and Lr24 have increased, whereas those to Lr14a, Lr16 and Lr17 have declined since 2000. The frequency of isolates virulent to Lr9 rose dramatically from 2.8% in 2006 to 8.7% in 2007. The frequencies of the two most predominant virulence phenotypes, TDBG (54.3%) and TDBJ (16.5%), remained unchanged from 2006, whereas the third most predominant phenotype MLDS increased from 1.4% in 2006 to 8.4% in 2007.