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Comparative Virulence of Monokaryotic and Dikaryotic Stages of Five Isolates of Uromyces appendiculatus. J. A. Kolmer, Graduate research assistant, Department of Plant Pathology, University of Minnesota, St. Paul 55108, Present address: Department of Plant Pathology, North Carolina State University, Raleigh 27650; B. J. Christ(2), and J. V. Groth(3). (2)(3)Graduate research assistant, and associate professor, respectively, Department of Plant Pathology, University of Minnesota, St. Paul 55108, (2)Present address: Department of Botany, University of British Columbia, Vancouver, Canada V6T 2B1. Phytopathology 74:111-113. Accepted for publication 25 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-111.

The virulence of monokaryotic basidiospores and dikaryotic aeciospores and urediniospores of five isolates of Uromyces appendiculatus was compared on 11 lines and cultivars of beans (Phaseolus vulgaris). Virulence of monokaryotic basidiospores of each isolate was determined by placing germinating teliospores over plants of each line or cultivar. Segregating isolates produced both pycnia and flecks; homozygous isolates produced only flecks or pycnia. The fungal isolates were mass-selfed and the bean lines inoculated with bulked S1 aeciospores to detect heterozygosity and dominance in the dikaryotic stage. Segregating dikaryotic S1 aecial collections gave rise to both flecks and uredinia; homozygous isolates produced only flecks or uredinia. With only two exceptions, in which avirulent basidiospores produced no reaction, isolates that segregated for pycnial infection types also segregated as dikaryotic S1 aeciospores, and isolates that did not segregate as monokaryons did not segregate as S1 aeciospores.

Additional keywords: bean rust, genetics, necrotic fleck, telia, uredinia.