Printed in Great Britain A Cytological Comparison of Inclusions as a Basis for Distinguishing Two Filamentous Legume Viruses

Light and electron microscopy were used to compare two flexuous-rod viruses: cowpea virus (CV) and bean yellow mosaic virus (BYMV). Inclusions induced by CV were consistently different from those induced by BYMV. In the light micro-scope, BYMV-induced cylindrical inclusions appeared as a group of plates, whereas CV-induced cylindrical inclusions appeared as a group of tubes. Electron micro-scopy showed that CV induced fibrous nuclear inclusions, while BYMV induced non-fibrous nucleolar inclusions in Crotalaria spectabilis. Thin section studies showed that CV-induced cylindrical inclusions contained circles and tubes, but no laminated aggregates, while BYMV-induced cylindrical inclusions contained laminated aggregates, but no circles or tubes. The shapes of extracted inclusions induced by CV were consistently different from those induced by BYMV. These viruses are cytologically different and are believed to be distinct