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A Study of Race Populations of Puccinia recondita f. sp. tritici. H. C. Young, Jr., Professor, Department of Plant Pathology, Oklahoma State University, Stillwater OK 74074; J. M. Prescott, Former Research Assistant, Oklahoma State University, now Pathologist, The Rockefeller Foundation, Wheat Research and Training Center, Ankara, Turkey. Phytopathology 67:528-532. Accepted for publication 9 November 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-528.

Uredial samples of the wheat leaf rust fungus were collected from a susceptible cultivar at 20 sites in Oklahoma. From 647 isolates of that uredial population eight races based on Unified Numeration (UN) differential cultivars, or 17 races based on North American Wheat Leaf Rust Research Workers Committee (NA65) differential cultivars were found. Telial samples from the same uredial population were used to produce aecia on Thalictrum speciosissimum or T. dasycarpum. Identification of races of the resulting uredia produced 24 races based on UN differentials and 25 races based on the NA65 differentials. Thus, in the original uredial population in the field, most of the genes conditioning avirulence must have been heterozygous since the uredia from the aecia either were F1ís or were the result of selfing.