How important is genome division as a taxonomic criterion in plant virus classification?

The number of nucleic acid components that constitute a virus genome has been used as an important discriminatory character in defining groups of plant viruses. However, with some virus groups, in particular potyviruses, recent results of nucleotide sequencing have reinforced previously deduced tentative relationships among viruses with different numbers of genome parts. A convenient solution is to classify these different types into groups or genera within a family (e.g. Potyvirus and Bymovirus in the family Potyviridae).