Improvement of Grafted Watermelon Transplant Survival as a Result of Size and Starch Increases Over Time Caused by Rootstock Fatty Alcohol Treatment: Part I

Abstract

Application of fatty alcohol to rootstocks used for vegetable grafting has been shown to increase the efficiency of producing grafted transplants by controlling cucurbit (Cucurbitaceae) rootstock meristematic regrowth and by allowing the rootstocks to accumulate carbohydrates, especially starch, over time in the hypocotyl and cotyledon. A grafting experiment was conducted to determine the effect of increased carbohydrates on survival of watermelon (Citrullus lanatus) grafts using standard grafting procedures. ‘Carnivor’ interspecific hybrid squash (Cucurbita maxima × C. moschata) and ‘Macis’ bottle gourd (Lagenaria sicereria) rootstocks at 1, 7, 14, and 21 days after fatty alcohol treatment were grafted with ‘Tri-X 313’ seedless watermelon using the one-cotyledon method. Graft survival on ‘Macis’ rootstock was acceptable or significantly increased up to day 14, with a slight decrease at day 21. Graft survival on ‘Carnivor rootstock was also acceptable up to day 21, with a significant increase between days 1 and 7. The second experiment was conducted to determine whether the increased carbohydrates provide sufficient energy to successfully graft without the rootstock cotyledon, a method that has previously shown inconsistent results. Graft survival was improved by 90% using treated ‘Carnivor’ rootstock 7 days after fatty alcohol treatment and ‘Macis’ rootstock 14 days after fatty alcohol treatment. Adoption of the hypocotyl-only graft method in commercial production may increase efficiency by better using greenhouse space and could decrease disease probability by removing the cotyledons before grafting.