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

item Kousik, Chandrasekar - Shaker

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2006
Publication Date: 7/8/2007
Citation: Kousik, C.S., Hassell, R.A. 2007. Evaluation of Commercial Watermelon Rootstocks for Tolerance to Phytophthora Blight. Phytopathology. 97:S182.

Interpretive Summary:

Technical Abstract: Phytophthora blight and fruit rot caused by Phytophthora capsici is becoming an important and emerging disease of watermelons (Citrullus lanatus). The disease mainly occurs in low lying areas of the fields where water logged conditions may be present. In recent years, the practice of grafting seedless watermelons (triploids) onto rootstocks belonging to other Cucurbitaceae genera is gaining importance. We evaluated five week old plants of commercial rootstocks for tolerance to Phytophthora blight by inoculating them with a zoospore suspension (10,000 zoospores/ml/plant) consisting of a mixture of seven isolates of P. capsici in the greenhouse. Commercial rootstocks called Macis and Emphasis were tolerant to Phytophthora blight compared to RS-1330, PST04-109W and Shintosa-Camel. Similarly triploids grafted on Emphasis appeared to be tolerant compared to the susceptible cultivar black diamond. As a part of our new program, we will be conducting further studies in a P. capsici infected field to test the effectiveness of rootstocks and grafts and also screen plant introductions of various cucurbit genera to identify resistant rootstocks.