The Effect of Rootstock Age on Grafting Ability, Re-rooting, and Field Performance of Grafted Watermelon Transplants

Fatty alcohol treatment is a useful technology that prevents rootstock regrowth in Bottle Gourd (Lagenaria siceraria) and Interspecific Hybrid Squash (Cucurbita maxima x C. moschata) rootstocks.  During a three-week period after treatment, rootstock carbohydrates have been shown to increase.  This increase could provide energy to improve graft healing and rootstock re-rooting.  This positive effect on transplant quality could lead to an eventual improvement in overall fruit quality and yields.   A greenhouse grafting experiment and an open-field trial were conducted to characterize this effect.   Bottle Gourd (cv. ‘Macis’) and Interspecific Hybrid Squash (cv. ‘Carnivor’) rootstock seed were sown in subsequent weekly plantings to achieve rootstock ages of 1, 7, 14, and 21 days after fatty alcohol application.  All rootstocks were grafted using Tri-X 313 scion.  The age of the scion was the same for all rootstock types, and the grafting was done on the same day using the one-cotyledon grafting method.  Two weeks after grafting, the percentage of healed grafts was calculated and scion fresh and dry weights were recorded.   Rooting percentage, root length density (RLD), and surface area (SA) were also measured.  Increases for both cultivars were observed as rootstock age increased.  Grafted plants were also planted in a field at the Clemson University Coastal Research Station in Charleston, SC.  Transplant survival was recorded and aerial tissue fresh and dry weights from two plants per plot were measured.  Yield data, including number and weight of fruit produced per plot and number of harvests per plot, was also collected. Significant effects in both plant growth and fruit yields were observed depending on the age of the rootstock treatments.