HortScience (2005) 40, 154-156

Claude E. Thomas, Amnon Levi and Ellis Caniglia (2005)
Evaluation of U.S. plant introductions of watermelon for resistance to powdery mildew
HortScience 40 (1), 154-156
Abstract: Two hundred sixty-six Citrullus lanatus (Thumb.) Matsum. and Nakai accessions (Plant Introductions and named cultivars) were tested against a race 2 Sphaerotheca fuliginea (Schlechtend.: Fr.) Pollacci isolate to evaluate for resistance to powdery mildew disease. Growth room-grown seedlings were artificially inoculated with conidia from watermelon host leaves at 2-day intervals from the appearance of the first true leaf until test results data were taken, when the second true leaf was fully expanded. Plants were evaluated on a 1 to 9 scale of increasing disease severity. Disease indices (DIs) were calculated as weighted averages for each entry. All genotypes with resistant plants (powdery mildew rating 1 to 3) were reevaluated in a replicated test of 3 replications of 10 plants each. Disease indices were again calculated. Twenty-two plant introductions (PIs) and one named variety displayed intermediate resistance to powdery mildew in the replicated test with DIs ranging from 5.0 to 6.0.
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Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Podosphaera fuliginea
	Podosphaera xanthii	Watermelon/colocynth (Citrullus)