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Electron Microscopy of Petunia Vein-Clearing Virus, an Isometric Plant Virus Associated with Specific Inclusions in Petunia Cells. D. Lesemann, Virologist, Biologische Bundesanstalt für Land- und Forstwirtschaft, 33 Braunschweig, Messeweg 11/12, Germany; R. Casper, Virologist, Biologische Bundesanstalt für Land- und Forstwirtschaft, 33 Braunschweig, Messeweg 11/12, Germany. Phytopathology 63:1118-1124. Accepted for publication 16 March 1973. DOI: 10.1094/Phyto-63-1118.

Ultrathin sections of petunia cells infected by petunia vein-clearing virus revealed rounded inclusion bodies a few µm thick. They showed a heavily contrasted, finely granular matrix containing lightly contrasted vacuole-like regions. No membranes were associated with the inclusion body structures. Virus particles occurred in distinct regions of the infected cells, often near the inclusion bodies, but have not been found within the matrix of the inclusion bodies. Conspicuous elements of endoplasmic reticulum were associated with the virus-containing regions and were sometimes arranged in several concentric layers. The diameters of the virus particles were 43 nm in negatively stained crude extracts and about 46 nm in ultrathin sections.