Cytopathological Changes of Pea Plants Infected with Pea Stem Necrosis Virus

Abstract

Pea stem necrosis virus (PSNV) particles were isometric and 34 run in diameter, and showed rounded outlines with rough surfaces when they were examined in electron microscope after negative-staining using uranyl acetate. In ultrathin sections, large numbers of virus particles were consistently scattered within the ground cytoplasm in cells of most tissues of infected pea leaves. Crystalline arrays of virus particles were observed only in necrotic cells. No virus particles were detected in nuclei, chloroplasts or mitochondria. A characteristic feature in infected cells was the formation of small vesicles, bounded by a single membrane, at the peripheries of the mitochondria which are superficially quite similar to multivesicular bodies induced by some other plant viruses. Possible affinities of PSNV with the tombusvirus group are discussed and it is suggested that PSNV may be grouped with certain other single-component viruses such as carnation mottle or galinsoga mosaic viruses.