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Title: Fruit age and development of Phytophthora fruit rot on resistant and susceptible watermelon lines

item Kousik, Chandrasekar - Shaker
item Ikerd, Jennifer
item Turechek, William

Submitted to: Cucurbitaceae Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/27/2014
Publication Date: 10/12/2014
Citation: Kousik, C.S., Ikerd, J.L., Turechek, W. 2014. Fruit age and development of Phytophthora fruit rot on resistant and susceptible watermelon lines. Cucurbitaceae Proceedings. Bay Harbor, MI. pp 35-37.

Interpretive Summary: N/A

Technical Abstract: Phytophthora fruit rot caused by Phytophthora capsici is an emerging disease in most watermelon producing regions of Southeast U.S. and has resulted in severe losses to watermelon growers especially in GA, SC, and NC. We recently released four germplasm lines (USVL203-PFR, USVL020-PFR, USVL782-PFR, and USVL489-PFR) with high levels of resistance to Phytophthora fruit rot for use in breeding programs. To evaluate these lines further, plants of each of these along with fruit rot susceptible cultivars were planted at weekly intervals for five consecutive weeks. Flowers were routinely inspected and pollinated to produce fruit of differing ages. Fruit from all plants of varying ages were harvested on the same day and inoculated with a 5-mm agar plug from an actively growing colony of P. capsici. Inoculated fruit were maintained in a room with >95% RH for five days after which data on disease development (lesion diameter, pathogen growth, & sporulation intensity) was recorded for each fruit. Fruit of susceptible checks (Sugar Baby and PI 536464) were susceptible, and the resistant germplasm lines were resistant at all fruit ages. Significantly lower amounts or no P. capsici DNA was detected in fruit tissue of the resistant germplasm lines compared to the susceptible lines using qPCR at all fruit ages. Our results suggest that, resistance or susceptibility to Phytophthora fruit rot in watermelon is not correlated with fruit age.