RECENT ASPECTS OF THE USE OF CYTOPATHOLOGY IN VIRUS IDENTIFICATION

Virus encoded nonstructural proteins and the effects of viral infections on the host cells membrane system are interpreted as examples of cytologically detectable characteristics of plant viruses which are independent from the traditionally determined properties of the coat protein. They are, therefore, valuable additional characters for virus identification and classification. The significance of accumulations of gene products is decribed for tobamo- and potyvirus-infected cells. Three principal types of membrane alterations are described. The occurrence of two types of small, ds-RNA containing vesicles among ss (+) RNA viruses is reviewed. Preliminary indications are shown for a correspondence of the vesicle types formed with supergroups of viruses which have recently been proposed on the basis of molecular interviral homologies.