The Plant Viruses: Polyhedral Virions with Tripartite Genomes

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 grou...