Virulence Patterns of Geographically Differing Isolates of Pyrenophora tritici-repentis and Sources of Resistance in Wheat. D. N. Sah, AvH Research Fellow, Institute of Plant Pathology and Plant Protection, Georg-August University, Grisebachstrasse 6, D-3400 Göttingen, Germany. H. Fehrmann, Professor, Institute of Plant Pathology and Plant Protection, Georg-August University, Grisebachstrasse 6, D-3400 Göttingen, Germany. Plant Dis. 76:712-716. Accepted for publication 2 January 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0712.

Nineteen single-conidiospore isolates of Pyrenophora tritici-repentis were isolated from leaf samples of wheat collected from Brazil, Germany, India, and Nepal, and one ascospore isolate was obtained from the United States for a virulence analysis study. Eight wheat cultivars were inoculated with a conidial suspension from each isolate, and percent necrotic leaf area was measured 5–6 days later using video image analysis. A highly significant interaction was found between cultivars of wheat and isolates of P. tritici-repentis. Cluster analysis of the data indicated only a moderate variation in virulence among the isolates of P. tritici-repentis tested. In a host resistance study, a significant interaction between 21 wheat lines and four geographically differing isolates also was detected. In a greenhouse study, 61 spring and 34 winter genotypes were evaluated for resistance to P. tritici-repentis. When 21 genotypes were reevaluated in a growth chamber with four isolates, 12 winter and six spring wheat cultivars and lines were resistant to moderately resistant.

Keyword(s): Drechslera tritici-repentis, physiologic race, stable resistance.