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Reduced Growth of Erysiphe graminis f. sp. hordei Induced by Tilletiopsis pallescens. A. L. Klecan, Visiting research specialist, Michigan State University (MSU)-Department of Energy (DOE) Plant Research Laboratory, Michigan State University, East Lansing 48824-1312; S. Hippe(2), and S. C. Somerville(3). (2)Professor in plant pathology, Christian Albrecht?s University Kiel, Institute of Botany, D-2300 Kiel 1, Federal Republic of Germany; (3)Assistant professor, MSU-DOE Plant Research Laboratory and Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824-1312. Phytopathology 80:325-331. Accepted for publication 20 September 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-325.

The leaf epiphyte, Tilletiopsis, which possesses hyaline ballistoconidia, was found contaminating barley seedlings infected with the obligate parasite Erysiphe graminis f. sp. hordei. The contaminant was identified as an isolate of the rare Tilletiopsis pallescens based on morphological, physiological, and biochemical characteristics. An antagonistic relationship between E. g. hordei and T. pallescens was demonstrated on the surface of barley leaf segments. On a gross level, T. pallescens caused severe reduction of mycelial expansion and spore production by E. g. hordei, whereas T. minor was antagonistic to a lesser extent. Low-temperature scanning and conventional transmission electron microscopy showed that hyphae of E. g. hordei were collapsed and degenerated in the presence of T. pallescens.

Additional keywords: biocontrol, isozyme, mycoparasite, powdery mildew.