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ARS Home » Southeast Area » Charleston, South Carolina » Vegetable Research » Research » Publications at this Location » Publication #348638

Research Project: Biology, Etiology and Host Resistance in Vegetable Crops to Diseases and Nematodes

Location: Vegetable Research

Title: Relative susceptibility of commercial watermelon varieties to powdery mildew

item Kousik, Chandrasekar - Shaker
item Ikerd, Jennifer
item MANDAL, MIHIR - Oak Ridge Institute For Science And Education (ORISE)

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2018
Publication Date: 2/14/2018
Citation: Kousik, C.S., Ikerd, J.L., Mandal, M.K. 2018. Relative susceptibility of commercial watermelon varieties to powdery mildew (Abstr.) Phytopathology 108:S2.6.

Interpretive Summary:

Technical Abstract: Powdery mildew (PM) of watermelon caused by Podosphaera xanthii has been occurring frequently in recent years and growers routinely apply fungicides to manage PM. The current study was conducted over three summers from 2014, to 2016 to determine the relative susceptibility of twenty eight watermelon varieties to P. xantii populations prevailing in Charleston, South Carolina. USVL677-PMS, highly susceptible to PM and USVL531-MDR resistant to PM were included as controls in all three years. A randomized complete block design with three replications was used each year and plants were rated on a modified Horsfall-Barrett scale of 0-10 of increasing disease severity. During all three years USVL677-PMS was the most susceptible line with the highest AUDPC and abundant PM conidia on the lower leaves. In comparison USVL531-MDR was practically immune and resistant. The commercial pollenizers SP5, SP6 and Lion were all resistant to PM. Among the red fleshed varieties, Suprema a seedless watermelon was relatively resistant. Most of the seeded varieties evaluated (e.g. Malali, Black Mama, Mickey Lee) were highly susceptible to PM. Similar results were also obtained in growth chamber studies where the plants were inoculated with P. xanthii conidia (105 conidia-ml). Currently very few to no PM resistant varieties are available and there is a need to develop newer resistant varieties for use by watermelon growers.