Squash vein yellowing virus: a new virus of cucurbits in the USA
During a survey on cucurbit viruses conducted in Florida (US), a new virus was found in a sample taken from a squash plant (Cucurbita pepo) showing vein yellowing symptoms. This new virus was tentatively called Squash vein yellowing virus (SqVYV) and assigned to the genus Ipomovirus in the family Potyviridae. Its experimental host range was limited to species in the family Cucurbitaceae. The most severe symptoms were observed on squash (C. pepo) and watermelon (Citrullus lanatus). In transmission experiments, SqVYV was transmitted by Bemisia tabaci but not by aphids (Myzus persicae) or seeds.
In the field, SqVYV was found to be associated with a severe vine decline and fruit rot of watermelon, which has been observed in southwest and south central Florida since 2003. Around harvest time, the foliage of affected plants turns yellow and entire plants rapidly wilt and collapse. Although there are no external symptoms, fruit of declining vines frequently show rinds with greasy and discolored (brown and/or watersoaked) internal blotches. The flesh is inedible and non-marketable. Yield losses of 50%-100% are not uncommon in affected fields. During glasshouse experiments, SqVYV was found sufficient to induce typical disease symptoms on C. lanatus. A limited survey revealed that SqVYV had been present during the last five growing seasons in watermelons suffering from the disease in Florida. Therefore, it is suggested that SqVYV is the likely cause of this new watermelon disease. In September 2006, moderate vine decline symptoms were observed on watermelon plants in a commercial field in Indiana. SqVYV was detected in infected plants. However, the disease is not considered as a serious threat in Indiana because the vector B. tabaci is relatively uncommon and the cold winter temperatures will not allow whitefly populations or SqVYV-infected watermelon plants to survive from one season to another.
Sources
Adkins S, Webb SE, Achor D, Roberts PD, Baker CA (2007) Identification and characterization of a novel whitefly-transmitted member of the family Potyviridae isolated from cucurbits in Florida. Phytopathology 97(2), 145-154.
Egel DS, Adkins S (2007) Squash vein yellowing virus identified in watermelon (Citrullus lanatus) in Indiana. Plant Disease 91(8) p 1056.
INTERNET (last retrieved in 2007-11).
National Watermelon Association. Whitefly (Bemisia tabaci) transmitted Squash vein yellowing virus (SqVYV): a component of watermelon vine decline in South Florida by PD Robert. http://www.nationalwatermelonassociation.com/scientific_whitefly.php
USDA-ARS. Research Projects.
Squash vein yellowing virus and its effects on watermelon. http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=209684
Squash vein yellowing virus, a novel ipomovirus, isolated from squash and watermelon in Florida. http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=201517