Suggestions for the classification and nomenclature of helical plant viruses.

Helical plant viruses are arranged into four families: Flexiviridae, Tobamoviridae, Hordeiviridae, and Tobraviridae. Further division of these families into genera and subgenera is shown. A family-specific, constant amount of RNA per unit virion length and a distinct radial location of RNA from the center of the helix are considered as basic criteria for establishment of these families.