Colony Color, Growth, Sporulation, Fungicide Sensitivity, and Pathogenicity of Pyrenophora tritici-repentis. R. M. Hunger, Associate Professor, Department of Plant Pathology, Oklahoma State University, Stillwater 74078-0285. D. A. Brown, Graduate Research Assistant, Department of Plant Pathology, Oklahoma State University, Stillwater 74078-0285. Plant Dis. 71:907-910. Accepted for publication 4 June 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0907.

Nine single-ascospore isolates (seven from the same ascus) of Pyrenophora tritici-repentis were characterized for colony color, growth on three media (potato-dextrose agar [PDA], clarified V-8 juice agar [CV-8], and a defined medium [DM]), sporulation, sensitivity to fungicides, and pathogenicity. Five isolates appeared dark on PDA, three appeared white, and one appeared cream-colored; one isolate that grew poorly on all media was omitted from further studies. White isolates and the cream-colored isolate showed the greatest growth (hyphal extension) on all media. Six isolates (five dark and the cream-colored isolate) sporulated profusely on CV-8, one sporulated at a low level, and two never produced conidiophores or conidia. Isolates were most sensitive to propiconazole, moderately sensitive to BAY 1608, and least sensitive to RH 3866. All isolates were pathogenic on wheat, and two white isolates and the cream-colored isolate generally produced the longest lesions on leaves of wheat seedlings.