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Cytology and Histology

Ultrastructure of Cells of Ulmus americana Cultured in Vitro and Exposed to the Culture Filtrate of Ceratocystis ulmi. Paula M. Pijut, Department of Horticulture, The Ohio State University, Columbus 43210, Present address: USDA-Forest Service, North Central Forest Experiment Station, 1992 Folwell Ave., St. Paul, MN 55108; R. Daniel Lineberger(2), Subhash C. Domir(3), Jann M. Ichida(4), and Charles R. Krause(5). (2)Department of Horticulture, The Ohio State University, Columbus 43210, Present address: Department of Horticulture, Clemson University, Clemson, SC 29634; (3)(4)(5)USDA-ARS, Nursery Crops Research Laboratory, Delaware, OH 43015. Phytopathology 80:764-767. Accepted for publication 12 February 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/Phyto-80-764.

Calli of American elm susceptible and resistant to Dutch elm disease were exposed to a culture filtrate of a pathogenic isolate of Ceratocystis ulmi. Cells from untreated tissue exhibited typical internal composition associated with healthy, actively growing cells. All cells exposed to culture filtrate showed appreciable ultrastructural changes. Cells from susceptible American elm displayed mitochondrial and cytoplasmic disruption. Damage to membranes was evident by the appearance of incomplete cell walls and distinctive plasmolysis. Cells of the resistant American elm differed dramatically with the presence and accumulation of phenoliclike deposits. The response seen with the resistant elm could be associated with a defensive mechanism against toxic metabolites of C. ulmi.