2018 ASHS Annual Conference

The production of grafted watermelon seedlings is labor-intensive and more costly to the propagator and grower than non-grafted seedlings. Rootstock regrowth, sometimes referred to as ‘suckering’, is a major concern for grafted watermelon as the commonly used grafting methods, one-cotyledon and hole insertion, often leave rootstock bud meristem tissue intact. Rootstock regrowth can result in scion abortion, graft failure, or a decrease in yield by robbing the scion of water and nutrients. Another challenge facing the watermelon grafting industry is grafting efficiency, especially the speed at which grafting occurs. Further, desiccation of the grafted seedling occurs because of water stress of the scion during healing and hardening after grafting, causing death of grafted seedlings. In this study, the splice grafting method was used where both rootstock cotyledons were removed to eliminate meristem tissue and rootstock regrowth. Antitranspirant products, which can increase stomatal resistance and mitigate water stress, were tested to determine if they could increase the survival of splice-grafted watermelon as compared to water control. Antitranspirant products Chitosan (0.08% solution), Root-Drench (2% solution), Moisture-Loc (10% solution) and Glycerin (4% solution) were applied as a drench or foliar spray to rootstock and scion seedlings 1 day before grafting. Survival (%) of splice-grafted watermelon seedlings 16 days after grafting was the greatest for plants that received Root drench and Glycerin treatment (70% and 57%, respectively), and was lowest for plants that received water (8%) (P = 0.0005). These results indicate that antitranspirant applications to rootstock and scion seedlings before grafting can increase grafting success, but further research is needed to optimize the environmental conditions for the survival of grafted plants.

Keywords. grafting efficacy, rootstock regrowth, transpiration, stomatal resistance