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Title: Influence of fruit age on Phytophthora fruit rot development on susceptible and resistant watermelon germplasm

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

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., Turechek, W. 2015. Influence of fruit age on Phytophthora fruit rot development on susceptible and resistant watermelon germplasm. Phytopathology. 105 (Suppl 4):S4.75.

Interpretive Summary: N/A

Technical Abstract: Phytophthora fruit rot of watermelon caused by Phytophthora capsici is an emerging disease in the southeastern United States. The disease has resulted in severe losses to watermelon growers in GA, SC, and NC, and is considered a top-research priority by the National Watermelon Association. We released four germplasm lines (USVL203-PFR, USVL020-PFR, USVL782-PFR and USVL489-PFR) with high levels of resistance to Phytophthora fruit rot. To determine influence of fruit age on disease development, resistant and susceptible lines were planted at weekly intervals for 5 consecutive weeks in a field in 2011, 2012 and 2013. Flowers were routinely inspected and pollinated to produce fruit of differing ages. Fruit of varying ages were harvested on the same day in each year and inoculated with a 5-mm agar plug from an actively growing colony of P. capsici. Inoculated fruit were maintained in a humid chamber (>95% RH, 26±2 °C) for 5 days after which data on disease development (lesion diameter & sporulation intensity) was recorded for each fruit. Fruit of susceptible checks (Sugar Baby and PI 536464) had significantly larger lesions and greater sporulation than fruit from resistant germplasm lines at all fruit ages. Significantly lower amounts of P. capsici DNA was detected in fruit tissue of resistant germplasm than susceptible checks at all ages. These results suggest that resistance to Phytophthora fruit rot in watermelon is not correlated with fruit age.