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Title: Evaluation of Commercial Watermelon Rootstocks for Tolerance to Phytophthora Blight and Watermelon Vine Decline

item Kousik, Chandrasekar - Shaker
item Adkins, Scott

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 1/30/2007
Publication Date: 7/2/2007
Citation: Kousik, C.S., Adkins, S.T., Roberts, P.D., Hassell, R. 2002. Evaluation of Commercial Watermelon Rootstocks for Tolerance to Phytophthora Blight and Watermelon Vine Decline. HortScience. 42(3):453.

Interpretive Summary:

Technical Abstract: Phytophthora blight and fruit rot caused by Phytophthora capsici, and watermelon vine decline (WVD) caused by Squash vein yellowing virus (SqVYV), are two important and emerging diseases of watermelons (Citrullus lanatus). Recently, the practice of grafting seedless watermelons (triploids) onto rootstocks of other Cucurbitaceae genera has been gaining importance for disease management. We first evaluated five-week old plants of commercial rootstocks without the scion for tolerance to Phytophthora blight by inoculating them with a zoospore suspension (10,000 zoospores/plant) consisting of a mixture of seven isolates of P. capsici in a greenhouse in Charleston, SC. Commercial rootstocks named Macis and Emphasis (Lagenaria spp.) were tolerant to Phytophthora blight compared to RS-1330, PST04-109W and Shintosa-Camel. Similarly, triploids grafted on Macis or Emphasis appeared to be tolerant compared to the susceptible cultivar Black Diamond or on other rootstocks. We mechanically inoculated a different set of the same rootstocks with SqVYV (causes WVD) in a greenhouse in Ft. Pierce FL. Rootstocks of Emphasis and Macis appeared to be tolerant to the virus compared with other rootstocks or the seedless watermelon Petite Perfection which was very susceptible. Though Emphasis and Macis rootstocks were tolerant to SqVYV, watermelon plants grafted on them were still very susceptible. Similarly, the grafted watermelon scions on all rootstocks were highly susceptible to WVD in the field in Immokalee, FL. We will be conducting further studies in the fields in Charleston, SC to test the effectiveness of rootstocks and grafts against P. capsici and similarly evaluate grafted watermelons for tolerance to WVD in Florida.