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Research Project: Development of Disease and Nematode Resistance in Vegetable Crops

Location: Vegetable Research

Title: Powdery mildew resistant cucurbit rootstocks confer tolerance to grafted susceptible watermelon scions

Author
item Kousik, Chandrasekar - Shaker
item Ikerd, Jennifer
item HASSELL, RICHARD - Clemson University

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/8/2015
Publication Date: 11/1/2015
Citation: Kousik, C.S., Ikerd, J.L., Hassell, R. 2015. Powdery mildew resistant cucurbit rootstocks confer tolerance to grafted susceptible watermelon scions. Phytopathology. 105 (Suppl 4):S4.75.

Interpretive Summary: N/A

Technical Abstract: Cucurbit powdery mildew (PM) caused by Podosphaera xanthii can impact seedling growth and cause serious losses in greenhouse and open fields. We have developed watermelon and bottle gourd germplasm lines with high levels of resistance to PM. A PM susceptible watermelon cultivar Mickey Lee (ML) was grafted on various PM resistant rootstocks. USVL677-PMS (watermelon) and USVL848-PMS (bottle gourd) were used as susceptible rootstock checks. Grafted plants were inoculated by spraying with a PM melon race 1 conidial suspension (2 x 104 conidia/mL) and rated for PM severity on a 0-10 scale about 2 weeks after inoculation. Trials were repeated in a greenhouse three times (2012-2014). Severe PM was observed on the cotyledons of USVL677-PMS and USVL848-PMS. Significantly less to no PM was observed on the cotyledons of PM resistant rootstocks. Severe PM was observed on plants of ML scion cotyledon that were grafted on susceptible rootstocks. Significantly (P=0.001) less powdery mildew was observed on the second true leaf of ML scions grafted on some of the PM resistant watermelon lines compared to those grafted on susceptible rootstocks. Not all PM resistant watermelon lines conferred resistance to true leaves of the susceptible scion. PM on the second true leaf and upper leaves was significantly less on ML scion grafted on two PM resistant bottle gourd rootstocks (USVL351-PMR and USVL482-PMR) and a hybrid rootstock. Resistant rootstocks may help manage PM of watermelon.