title: An ultrastructural investigation of the 'microsclerotia' formed in single cells of root cortical cells associated with corky root rot of tomato.
abstract: White and Scott (1973) described two forms of microsclerotia associated with corky root rot of tomato, one being formed in single cells of the outer root cortical cells and the other produced in culture from isolation of diseased roots and in degenerated root debris. By assuming that both forms were of fungal origin, they conducted an ultrastructural study using the microsclerotia produced in culture but not those formed in single cells. They demonstrated that the microsclerotia from culture consisted of hardened, interwoven hyphae of the fungus, Pyrenochaeta lycopersici. Since there have been doubts about the nature of the microsclerotia formed in single cells, an ultrastructural study was conducted. The results demonstrated clearly that the 'microsclerotia' formed in single cells of the root cortical cells were not composed of fungal mycelia, indeed these blackened cells or 'microsclerotia' were filled with numerous crystallines. There was no evidence of the presence of fungal hyphae in or around these cells. Both diseased and healthy, and young and old root cortex cells of many cultivars of tomato contained cells filled with crystallines. Therefore, it is clear that the 'microsclerotia' formed in single cells of the outer cortex described by White and Scott are not microsclerotia of the fungus, P. lycopersici.
authors.affiliation: Agriculture and Agri-Food Canada, Greenhouse and Processing Crops Research Centre, Harrow, Ontario N0R 1G0, Canada.
authors.forename: J C
authors.initials: JC
authors.lastname: Tu
authors.forename: B
authors.initials: B
authors.lastname: Harwood
mesh_terms: D005658:Fungi / Q000254:growth & development / Q000472:pathogenicity* / Q000648:ultrastructure*; D018551:Solanum lycopersicum / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000166:cytology / Q000382:microbiology* / Q000648:ultrastructure