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Title: Research Update on Mature Watermelon Vine Decline in South Florida

item Kousik, Chandrasekar - Shaker
item Adkins, Scott
item Bruton, Benny

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 12/8/2006
Publication Date: 12/13/2006
Citation: Kousik, C.S., Roberts, P.D., Adkins, S.T., Webb, S., Stansly, P.A., Baker, C., Bruton, B.D., Muchovei, R., Achor, D., Whidden, A.L. 2006. Research Update on Mature Watermelon Vine Decline in South Florida. Proceedings of the North Carolina Vegetable Grower's Association. 2006 Year Book Volume VIII:55.

Interpretive Summary:

Technical Abstract: Mature watermelon vine decline and fruit rot (MWVD) is a new, emerging disease that has caused devastating losses in the watermelon production region of southwest Florida since 2003 (Roberts et al., 2005). During the past few years, watermelon plants have been affected in each fall (September-December) and spring (January-May) season. Symptoms of MWVD typically occur at harvest time or one to two weeks prior to harvest when the vines decline rapidly. Foliage initially turns a slight yellow, then scorched and brown, followed by wilting and collapse of the entire vine, and severely affecting marketability of the fruits. The fruits appear normal on the outside, however, when cut, rind necrosis and degradation of the flesh are evident. Symptoms of MWVD are variable in that foliage decline symptoms can occur in the absence of fruit rot symptoms and vice-versa. Yield losses have been typically high; losses of 50%-100% are not uncommon in affected fields. Monetary loss due to vine decline has been estimated at $60 to $70 million in the past four years (Huber, 2006). Recent research (Adkins et al., 2006) identified a novel ipomovirus named Squash vein yellowing virus (SqVYV) associated with MWVD. In this study, it was also shown that SqVYV was transmitted by silver leaf whitefly (Bemisia tabaci, Biotype “B”). Symptoms of vine decline were observed in watermelon plants inoculated with SqVYV at different growth stages in the greenhouse. Similarly, watermelon plants that were mechanically inoculated with SqVYV at different growth stages in the field developed symptoms of vine decline. A field study conducted in the spring of 2006 in Immokalee, FL showed that watermelon plants grown adjacent to SqVYV-infected squash plants developed vine decline symptoms, including fruit rot, and eventually died. However, plants which were grown in the same field, but protected by screened cages to prevent infestation by whitefly, did not develop symptoms of vine decline. Preliminary analysis of declining watermelon plants in the field study detected the presence of SqVYV. Recent research to evaluate watermelon germplasm for resistance to SqVYV has identified some sources of resistance. Further experiments to confirm these preliminary field and greenhouse results as well as target management of vine decline by control of whiteflies are currently being conducted. Several other factors, including water stress, fungi and bacteria, that also have been implicated in eliciting rapid decline response of watermelon also are being investigated. Adkins, S., S.E. Webb, D. Achor, P.D. Roberts, and C.A. Baker. 2006. Identification and characterization of a novel whitefly-transmitted member of the family Potyviridae isolated from cucurbits in Florida. Phytopathology 96:In press. Huber, M. 2006. Taking vital vines. Citrus and Vegetable Magazine 70(6):22-24 (February issue). Roberts, P., R. Muchovej, D. Achor, C.A. Baker, B. Bruton, and S. Adkins. 2005. Investigation into a mature watermelon vine decline and fruit rot. Phytopathology 95:S89.