Saprophytic Growth and Pseudothecia Production byPyrenophora tritici-repentisin Plant Tissue Held at Controlled Water Potentials

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Abstract
Mycelial growth rate and production of pseudothecia by Pyrenopora 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.