Plaskitt, K.A. - John Innes Institute, Colney Lane, Norwich, England
The distribution of beet yellows virus (BYV) in local lesions of Chenopodium hybridum L. was studied by means of electron microscopy of thin sections. In the local lesions most cells close to the surface collapsed and their contents were found too dense to distinguish. Virus particles in aggregates of different size, some of them large and cross-banded, were found only as far as five cells down from epidermis. The chloroplasts in necrotic cells were observed to be markedly swollen, with a disordered thylakoid system. Convolute membraneous layers, apparently formed by scrolling of endoplasmic reticulum were occasionally found. Vesicles containing a fine network of fibrils appeared either singly or in clusters. Most of these ultrstructural features were similar to previously illustrated alterations in systemic hosts, thus providing further evidence for similar conformation of virus particles in systematic and hypersensitive hosts. The connection of some cytopathological symptoms to closterovirus classification is discussed.
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