Physiological specialization of Puccinia triticina, the causal agent of wheat leaf rust, in Canada in 2013

Wheat leaves infected with leaf rust collected across Canada in 2013 were used to isolate 265 Puccinia triticina Eriks. single uredinial isolates. When these were analysed for virulence on 16 standard differential wheat lines 38 virulence phenotypes were found, with MBDS (11.7%), TBBG (11.3%), TNBG (10.2%) and MBTN (8.3%) the most common. In Manitoba and Saskatchewan, 29 virulence phenotypes were found among 236 isolates, with MBDS (13.1%), TBBG (12.7%) and TNBG (11.4%) being the most common. From Ontario, four virulence phenotypes MBTN (73.7%), LCDN (10.5%), MGPS (10.5%) and TCRJ (5.3%) were determined among 19 isolates. There were 10 isolates from Prince Edward Island which grouped into seven different virulence phenotypes, the most common being MBNQ (three isolates) and MCNQ (two isolates). The frequencies of virulence to Lr9, Lr26, Lr3ka, Lr17, Lr30, Lr14a and Lr21 increased, and virulence to Lr2a, Lr2c, Lr16, Lr24, Lr11, Lr10 and Lr18 decreased, when compared with 2012. The increase in virulence frequency to Lr21 is important since many Canadian wheat cultivars have this gene, and could become more susceptible. There were no virulence phenotypes in common between Ontario and Prince Edward Island, and only one virulence phenotype from each of these regions was found in the larger sample from Manitoba and Saskatchewan, demonstrating the differences in the populations across Canada.