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Variations of Single-Basidiospore Isolates of Thanatephorus cucumeris. C. C. Tu, Graduate Assistant, Plant Pathology Department, University of Florida, Gainesville 32611; N. C. Schenck(2), and J. W. Kimbrough(3). (2)Professor, Plant Pathology Department, University of Florida, Gainesville 32611; (3)Associate Professor, Botany Department, University of Florida, Gainesville 32611. Phytopathology 64:1510-1512. Accepted for publication 18 June 1974. DOI: 10.1094/Phyto-64-1510.

Nineteen single-basidiospore isolates from a parent clone of Thanatephorus cucumeris were compared for their variability. The average growth rate at 25 C ranged 5.7-12.8 mm per day and optimum pH for mycelial growth was between 6.5 and 7.2. Isolates varied in their ability to form sclerotia on both potato-dextrose agar and in soil. Isolates varied from avirulent to moderately virulent. Fifteen isolates formed basidia on soil varying in the amount of hymenium produced and the size of basidial structures. Basidial shapes varied from subglobose to oblong and the ratio of average width of basidia to average width of supporting hyphae ranged from 1.5 to 1.9. The latter have ratios similar to those of Ceratobasidium.