VIEW ARTICLE

Cytology and Histology

Histopathology of Peronospora tabacina in Systemically Infected Burley Tobacco. R. D. Milholland, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650; J. Papadopoulou(2), and M. Daykin(3). (2)(3)Graduate research assistant, and research technician, respectively, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 71:73-76. Accepted for publication 29 July 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-73.

Field-grown burley tobacco plants (KY-14) systemically infected with Peronospora tabacina were examined histologically. The fungus was confined primarily to the vascular tissue in the stem, but caused severe necrosis of all tissues in diseased roots. The fungus progressed through the tissues intercellularly causing the host cell walls to collapse and eventually become necrotic. Intracellular hyphae were observed in xylem vessels and parenchyma cells. Single and branched haustoria also were observed. The fungus caused vascular plugging, hyperplasia of cambium and phloem, xylem disintegration, and the formation of vascular cavities. Infected stem and leaf tissues both contained mature oospores.