Rootstock Age Affects Grafting Ability and Rootstock Re-rooting of Grafted Watermelon Transplants

Regrowth from the rootstock of a grafted watermelon competes with the scion for nutrients and sunlight, and could cause yield loss and scion abortion.  Control of regrowth is costly and labor-intensive.  Fatty alcohol treatment of the meristem is a useful technology that prevents rootstock regrowth, thus reducing overall transplant costs.  During a three-week period after treatment, rootstock carbohydrates increase while plant growth is prevented.  This increase could provide needed energy to improve graft healing of the scion and encourage rootstock re-rooting.  A greenhouse grafting experiment was conducted to determine the effect of rootstock age after fatty alcohol treatment on graft healing and re-rooting.   Bottle Gourd (Lagenaria siceraria cv. ‘Macis’) and Interspecific Hybrid Squash (Cucurbita maxima x C. moschata 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, scion fresh and dry weights, percent rooting, root length density (RLD), surface area (SA), and number of forks were measured.   Significant effects of scion and rooting characteristics were observed over changes in rootstock age after fatty alcohol treatment.