The genome of yam virus X (YVX), a new member of the genus Potexvirus from yam (Dioscorea trifida), was completely sequenced. Structural and phylogenetic analysis showed that the closest relative of YVX is nerine virus X. A prevalence study found YVX only in plants maintained in Guadeloupe and showed that it also infects members of the complex D. cayenensis rotundata. This study provides evidence for the existence of two additional potexviruses, one of which infects D. nummularia in Vanuatu and the other, D. bulbifera and D. rotundata in Haiti and D. trifida and D. rotundata in Guadeloupe. This work also shows that existing potexvirus-specific degenerate primers targeting the ORF1-encoded polymerase domain are well suited for the identification of the three potexviruses reported here.