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Physiology and Biochemistry

Reciprocal Translocation of Carbohydrates Between Host and Fungus in Bahiagrass Infected with Myriogenospora atramentosa. K. T. Smith, Department of Plant Pathology, University of Georgia, Athens 30602, Current address for senior author: Department of Botany and Plant Pathology, University of New Hampshire, Durham 03824; C. W. Bacon(2), and E. S. Luttrell(3). (2)Department of Plant Pathology, University of Georgia, Athens 30602, Richard B. Russell Agricultural Research Center, U.S. Department of Agriculture, Agricultural Research Service, Athens, GA 30613; (3)Department of Plant Pathology, University of Georgia, Athens 30602. Phytopathology 75:407-411. Accepted for publication 5 November 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-407.

The pathogen Myriogenospora atramentosa provides an unprecedented model for the study of fungal biotrophy. Both mycelium and stromata of the fungus were entirely epiphytic upon the leaf blades of the host grasses Paspalum notatum and Andropogon virginicus, and both host and pathogen could be separated along their interface into separate homogeneous fractions for analysis. Successive opposing leaves of the host were commonly bound together at the tips by bridges of fungal stromata. Infected leaves contained less than 4% of the sucrose present in uninfected leaves. The primary carbohydrates present in stromatic extracts were the sugar alcohols mannitol and arabitol. An unidentified low-molecular-weight compound present in extracts of uninfected leaves and stromata was absent from extracts of infected leaves. Greater amounts of ¹⁴C label (originally supplied as ¹⁴CO₂) accumulated in compounds in infected leaves than in uninfected leaves. Compounds containing ¹⁴C label originally supplied as ¹⁴C-sucrose moved from leaf to stromatic bridge to second leaf. Although microscopy showed no alteration of the cuticle separating host and fungus, host epidermal cells beneath the fungus were modified in size and shape.