VIEW ARTICLE

Genetics

Evolution of Distinct Populations of Puccinia recondita f. sp. tritici in Canada. J. A. Kolmer, Research scientist, Agriculture Canada, Research Station, 195 Dafoe Road, Winnipeg, MB, Canada R3T 2M9; Phytopathology 81:316-322. Accepted for publication 17 September 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-316.

The eastern and prairie populations of Puccinia recondita f. sp. tritici in Canada had similar identities and frequencies of Unified Numeration (UN) races during the initial years of the annual wheat leaf rust survey (1931–1937) when susceptible cultivars were grown in both regions. Pathogenicity associations within each population also were very similar during this period. Differences between the eastern and prairie populations became evident after the introduction of leaf rust-resistant cultivars in the prairies in 1937. A series of resistant cultivars was released in this region, placing a continuous selection pressure on the corresponding virulences in the prairie leaf rust population. This resulted in cycles of selection and displacement of virulent and avirulent races, respectively, in this region. Susceptible cultivars continued to be grown in the eastern region, and the leaf rust population in this region has since had a different succession of UN races than the prairie population. The eastern and prairie populations of P. r. tritici are currently very different in terms of distinct phenotypes. These regional populations most likely originated from a common, introduced population of P. r. tritici, and the regional differences have resulted from the use of leaf rust-resistant and susceptible wheat cultivars.