Increasing Survival of Grafted Watermelon Transplants

Although grafting holds promise as a soilborne disease management strategy for watermelon production in Washington, it currently has significant limitations. Increased production costs related to grafting include the skilled labor needed for grafting, the special facilities that are required for the proper healing of the grafted plants, and unpredictable survival rate of grafted watermelon transplants. Studies with grafted tomato showed 98% survival by using a low cost healing chamber but watermelon graft survival was 80% as a result of the particular grafting technique (one-cotyledon splice) and the susceptibility of the plant to desiccation following the grafting procedure. The graft union for watermelon tends to be slow to heal (7 to 9 days) and the plant must rely on moisture in the air for survival during this time period. In 2015, a greenhouse experiment was conducted to investigate if application of commercial antitranspirant products (Moisturin film-forming, and Root-Zone stomata-closing), could increase the survival of grafted watermelon transplants. The one-cotyledon grafting method was used for grafting watermelon (cv. TriX Palomar) with rootstock (cv. Emphasis). The study utilized a randomized complete block design with 4 treatments and 5 replications, 12 plants per experimental unit, and was repeated two times. The treatments were applied one day before grafting: Moisturin (10% solution), Root-Zone (1.56% solution), Moisturin & Root-Zone (applied at the same respective rates), and a water control. The survival rate of grafted watermelon differed due to antitranspirants treatments (P < 0.0001). The treatment Moisturin + Root-Zone had the greatest survival rate (96%) while the Moisturin application had the lowest survival rate (55%), and Root-Zone treatment and water control had 88% and 73% survival rate, respectively. Results from this study indicate that survival rate of grafted watermelon transplants can be increased by using a combination of commercial antitranspirant products, Moisturin + Root-Zone, or application of Root-Zone only one day before grafting.

Key words: Grafting, Survival, Antitranspirant, Moisturin, Root-Zone