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Ultrastructural Comparison of Microbodies in Pathogenic and Saprophytic Hyphae of Fusarium oxysporum f. sp. lycopersici. William P. Wergin, Botanist (Plant Morphologist), Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705, Present address of author: ARS, USDA, Stoneville, Miss. 38776; Phytopathology 62:1045-1051. Accepted for publication 30 March 1972. DOI: 10.1094/Phyto-62-1045.

The fine structure of pathogenic fungal hyphae was examined in the vascular tissue of tomato plants inoculated with the Fusarium wilt organism, Fusarium oxysporum f. sp. lycopersici. Three to 5 days after inoculation, the hyphae were found localized in the metaxylem vessels of the tomato stems. In addition to the normal complement of fungal organelles, the cytoplasm of the fungus contained numerous, well-developed microbodies. A negative staining reaction with 3,3-diaminobenzidine indicated that these microbodies did not have peroxidase activity. The fungus was also cultured on potato-dextrose agar and processed for electron microscopic observation. Examination of this material disclosed that saprophytic hyphae did not contain the large microbodies which were commonly found in the pathogenic hyphae.

Additional keywords: peroxisomes, glyoxysomes, Fusarium wilt of tomato.