Fourth International Bemisia Workshop International Whitefly Genomics Workshop
Squash Vein Yellowing Virus, A Novel Ipomovirus, Isolated from Squash and Watermelon in Florida
1 USDA-ARS, Fort Pierce, FL, USA. Correspondence: SAdkins@ushrl.ars.usda.gov
2 University of Florida, Gainesville, FL, USA
3 University of Florida, Lake Alfred, FL, USA
4 USDA-ARS, Charleston, SC, USA
5 University of Florida, Immokalee, FL, USA
6 FDACS-DPI, Gainesville, FL, USA
A novel whitefly-transmitted member of the family Potyviridae was isolated from a squash plant (Cucurbita pepo) with vein yellowing symptoms in Florida. The virus, for which the name Squash vein yellowing virus (SqVYV) is proposed, has flexuous rod-shaped particles of ~840 nm in length. SqVYV was transmitted by whiteflies (Bemisia tabaci, biotype B) but was not transmitted by aphids (Myzus persicae). The experimental host range was limited to species in the Cucurbitaceae, with the most dramatic symptoms observed in squash and watermelon, but excluded all tested species in the Amaranthaceae, Apocynaceae, Asteraceae, Chenopodiaceae, Fabaceae, Malvaceae and Solanaceae. Initial greenhouse and field screening of watermelon germplasm with SqVYV has identified potential sources of resistance and experiments are in progress to confirm these preliminary observations. Infection of squash and watermelon by SqVYV induced inclusion bodies visible by electron and light microscopy that were characteristic of members of the family Potyviridae. Comparison of the SqVYV coat protein gene and protein sequences with those of recognized members of the family Potyviridae indicate that it is a novel member of the genus Ipomovirus. A limited survey revealed that SqVYV was present over the five most recent growing seasons in watermelons suffering from a mature vine decline and fruit rot observed in southwest and west central Florida. Inoculation of greenhouse-and field-grown watermelon plants with SqVYV at different stages of growth was sufficient to induce these symptoms, suggesting that it is the likely cause of this disease.