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Diversity of Virulence Phenotypes and Effect of Host Sampling Between and Within Populations of Puccinia recondita f. sp. tritici in Canada. J. A. Kolmer, Research Scientist, Agriculture Canada Research Station, 195 Dafoe Road, Winnipeg, Manitoba R3T 2M9 Canada. . Plant Dis. 76:618-621. Accepted for publication 5 February 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0618.

The phenotypic diversity between and within different groupings of Puccinia recondita f. sp. tritici isolates in 1990 in Canada was determined. The diversity and prevalence of virulence phenotypes were compared in collections from resistant and susceptible cultivars in the prairie provinces and from winter and spring wheats in the eastern provinces. The eastern P. r. tritici population (Quebec and Ontario) was dominated by one virulence phenotype at 57%, and 25 other phenotypes occurred at less than 10% each. Virulence phenotype frequencies were more evenly distributed in the prairie (Manitoba and Saskatchewan) population, although only 16 phenotypes were detected in this population. The eastern, prairie, and British Columbia populations had distinctly different leaf rust virulence phenotypes. Collections from Alberta resembled those from the prairie region more than they resembled those from British Columbia. In the eastern population, collections sampled from Ontario and Quebec were significantly different in frequency of virulence phenotypes, as were collections from winter and spring wheats, indicating that this population was composed of two components—one that overwinters on winter wheats and one that migrates from the Great Plains and is found primarily on spring wheats in this region. In the prairie region, collections from Manitoba and Saskatchewan were not significantly different, confirming that these provinces could be considered as a single epidemiological unit in 1990. There also were no significant differences between collections sampled from susceptible and resistant wheats in the prairie region or from nurseries or commercial wheat fields.

Keyword(s): epidemiology, Triticum aestivum, wheat leaf rust.