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Fine-Structure Analysis of Host-Parasite Relations in the Spot Anthracnose of Desmodium. David L. Mason, Associate Professor, Department of Biology, Wittenberg University, Springfield, OH 45501; and Research Plant Pathologist, Agricultural Research Service, U. S. Department of Agriculture (USDA) and Adjunct Professor, Ohio State University, Columbus, OH 45501; Charles L. Wilson, Agricultural Research Service USDA, North Central Region, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster, OH 44601. Phytopathology 68:65-73. Accepted for publication 6 July 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-65.

The pathogen Elsinöe wisconsinensis grows intercellularly in Desmodium illinoense. Host cells in close association with the pathogen undergo extensive hypertrophy and hyperplasia. The only cells destroyed are the epidermal cells which become enveloped by mycelia and crushed by the developing stroma. Chloroplasts in parasitized cells are smaller than normal, contain fewer grana and thylakoids per granum, and they generally lack starch granules. The number of Golgi bodies and Golgi vesicles are more abundant, and they reside in those parts of host cells associated with hyphae. Pinocytic vesicles containing a granular to fibrillar material occur abundantly in parasitized cells. These vesicles appear to pass through the hyaloplasm, and become enclosed in a second membrane originating from the tonoplast. They ultimately become deposited in the central vacuole, where they are broken down, and their contents are digested. Golgi vesicles fuse with newly formed and migrating pinocytic vesicles, the plasmalemma, and the tonoplast. The uninucleate intercellular fungal cells contain most of the organelles common to eucaryotes. Spherosome contents and glycogen granules are present in the fungal cell vacuoles, where they appear to be digested.