Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 2/4/2014
Publication Date: N/A
Interpretive Summary: N/A
Technical Abstract: Phytophthora fruit rot (PFR) and powdery mildew (PM) on watermelon can be devastating and significantly reduce fruit yield under favorable conditions. In recent years, these two diseases have become more common in the southeastern United States. Based on previous literature, we selected 35 watermelon plant introductions (PI) with varying levels of resistance to PM (Podosphaera xanthii, melon race 1 and 2). These PIs were evaluated for resistance to PM in the greenhouse from 2011-2013. Because of variability in resistance to PM, highly resistant plants were selected each year to develop multiple disease resistant watermelon germplasm. Mature watermelon fruit from PM resistant lines were inoculated with a local isolate of Phytophthora capsici and evaluated for resistance to PFR in a humid chamber (>96% RH, 26±2º C). The PI were also evaluated in the field (summer and fall 2012, 2013) against a PM melon race 1 (1W) strain prevalent in Charleston, SC. PI 269677 and Mickey Lee were used as PM and PFR susceptible checks. Mature fruit harvested from the field were also evaluated for PFR resistance. After three cycles of screening and selections, we have developed several watermelon germplasm lines from PIs by pure line selection with uniform PM and/or PFR resistance (e.g. PI 560020, PI 189225, PI 186489, PI 532738). The PM resistance is expressed in hypocotyls, cotyledons, and true leaves of young watermelon seedlings in the greenhouse and adult plants in the field. Some of the PIs were also resistant to anthracnose in two field evaluations. The PM and PFR resistant germplasm lines that are being developed may be used for developing resistant varieties and rootstocks for grafting watermelon.