Cytological and molecular evidence that the whitefly-transmitted cucumber vein yellowing virus is a tentative member of the family Potyviridae

Cucumber vein yellowing virus (CVYV) is widespread in cucurbits in the Midd le East. CVYV has filamentous particles and is transmitted by Bemisia tabac i by the semi-persistent mode. It has not yet been assigned to a specific g enus or family. Ultramicroscopic observations revealed numerous cylindrical cytoplasmic inclusions in melon and cucumber cells infected by CVYV isolat es from Israel and Jordan. Depending on the section orientation, the inclus ions appeared as pinwheels or as bundles. In addition, a 1.9 kb DNA fragmen t was amplified by RT-PCR from CVYV-infected plant extracts using primers d esigned to detect all potyvirids. Sequence comparisons with the amplified f ragment indicated that CVYV is more closely related to Sweet potato mild mo ttle virus than to any other virus in the family Potyviridae. These results suggest that CVYV can be considered as a tentative new member of the genus Ipomovirus, family Potyviridae.