This order of predominantly plant viruses is based on the properties of the Turnip yellow mosaic virus. The species have positive sensed, single stranded and monopartite RNA genomes. Expression of the genome does not involve DNA intermediates. The viruses of most families have flexible, filamentous particles. However, the particles of the type family Tymoviridae are icosahedral.
The following families are included under the Tymovirales: