Exogenous Treatments to Enhance Splice-Grafted Watermelon Survival

This study evaluated the use of splice grafting as a propagation strategy for watermelon. In experiment 1, the treatments consisted of sucrose, antitranspirant A, antitranspirant B, auxin (indole-3-butyric acid (IBA)) at two concentrations (10 and 20 mg·L−1), plus a water control. The survival (%) of splice-grafted watermelon plants differed due to the number of days after grafting and treatment (p < 0.0001, for both). At 21 days after grafting, plants treated with sucrose and antitranspirant A, and sucrose and antitranspirant A with 10 mg·L−1 auxin had 90% and 88% survival, respectively, whereas the graft survival was 18% for plants treated with water. Experiment 2 included the three top performing treatments from experiment 1 and a water control treatment, applied to both root-intact and root-excised rootstocks. There was a significant difference in survival (%) of splice-grafted watermelon due to root treatments, exogenous treatments, and the number of days after grafting (p < 0.0001, for all). At 21 days after grafting, survival for root-excised grafted plants was 11% lower compared to root-intact plants. Plants treated with sucrose and antitranspirant A, and sucrose and antitranspirant A with 10 mg·L−1 auxin had 87% and 86% survival, respectively, whereas plants treated with water had 14% survival. The external application of auxin applied to rootstock seedlings does not appear to be cost-effective; however, other products should be evaluated.