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Ecology and Epidemiology

Saprophytic Growth and Pseudothecia Production by Pyrenophora tritici-repentis in Plant Tissue Held at Controlled Water Potentials. W. F. Pfender, Assistant professor, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506; C. A. Pacey, and W. Zhang. Research assistant, and Graduate research assistant, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506. Phytopathology 78:1205-1210. Accepted for publication 18 April 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1205.

Mycelial growth rate and production of pseudothecia by Pyrenophora tritici-repentis in dead wheat leaves at a range of water potentials was measured. In sterilized, reinoculated leaves the fungus grew maximally at the wettest level tested (0.5 MPa = 5 bars) and was able to grow at a slow rate at 10.5 MPa. In infected nonsterile leaves, growth rates were slower than in sterilized leaves at all water potentials, and growth was detected at 8.5, but not at 10.5 MPa. Pseudothecia production in nonsterile leaves was equivalent to that in sterilized leaves. Production of pseudothecia was maximum at 0.5 MPa (wettest level tested), was significantly reduced at 1.6 MPa, and was limited to a very few, small ascocarps at 2.4 MPa; none were produced at 3.8 MPa.

Additional keywords: tan spot, Triticum aestivum, wheat.