The Fifth Report of the International Committee on Taxonomy of Viruses (ICTV), summarizes the proceedings and decisions reached by the ICTV at its meetings held at the International Congresses of Virology in Sendai (1984), Edmonton (1987) and Berlin (1990). This report has been organized in the same way as the previous ones (Wildy, 1971; Fenner, 1976; Matthews, 1979; 1982), yet it encompasses many more families and groups of viruses than previous reports, and it includes new tables, diagrams and keys. The officers and members of the ICTV study groups from 1984 to 1990 are listed, as the...

It has been known for a long time that the majority of plant viruses contain RNA and in the past decade and a half it has been realized that many have genomes consisting of three molecules of single-stranded RNA with positive polarity. Among these are viruses belonging to four groups recognized by the International Committee for Virus Taxonomy: the Bromovirus and Cucumovirus groups whose genomes are encapsi dated in small icosahedral particles or the Ilarvirus and alfalfa mosaic virus groups with spheroidal or bacilliform particles. In addition to their tripartite genomes, these viruses share...