ARS | Publication request: Patterns of Multi-Virus Infections in Florida Watermelon

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2008
Publication Date: July 1, 2008
Citation: Turechek, W., Adkins, S.T., Kousik, C.S., Stansly, P.A., Roberts, P.D. 2008. Patterns of Multi-Virus Infections in Florida Watermelon. Phytopathology. 98(6):S154

Technical Abstract: The whitefly-transmitted viruses Squash vein yellowing virus (SqVYV) and Cucurbit leaf crumple virus (CuLCrV) have had serious impact on watermelon production in west-central and southwest Florida in recent years. We collected plants randomly from a commercial watermelon field in southwest Florida showing symptoms of SqVYV and CuLCrV and cut cross sections from each vine on every plant from the crown to the vine tip. The cross sections were blotted onto nitrocellulose membranes and nucleic acid hybridization was used to test for the presence of SqVYV and CuLCrV. Results showed that SqVYV and CuLCrV were present in the field in approximately 38% and 45% of the plants collected in the field, respectively. In plants diagnosed with SqVYV, the presence of SqVYV in vine tissue decreased proportionately with increasing distance from the crown. In contrast, the growing tip was the single best tissue for detection of CuLCrV in plants diagnosed with CuLCrV. The results show that SqVYV and CuLCrV are spatially separated in watermelon plant tissue. In a separate study, we monitored the progress of SqVYV and CuLCrV in a 2.5 acre experimental field of ‘Fiesta’ located in Immokalee, FL. Symptoms of CuLCrV were present soon after planting. Symptoms of SqVYV first appeared 7 weeks after planting and by week 12 the field was fully collapsed from disease. Analyses indicated that the degree of association between the two diseases was not greater than what would be expected from random, and that SqVYV was distributed randomly at low incidences, but became progressively more aggregated as disease incidence increased. These results are an indication that the viruses are being introduced independently by whiteflies, although the whiteflies may be emigrating from the same source, with secondary spread being dominated by local or within-field populations of whiteflies. This is conceivable based on the spatial separation of the viruses in individual watermelon plants from the commercial field. Additional field surveys are in progress to verify and extend these findings.