Quality and Postharvest Performance of Watermelon Fruit in Response to Grafting on Interspecific Cucurbit Rootstocks

Grafting on disease‐resistant rootstocks is a growing practice in watermelon cultivation worldwide. Reports on effects of grafting on watermelon fruit postharvest performance are scarce. The current work examined postharvest performance at 25C of four diploid cultivars grown nongrafted or grafted onto three Cucurbita maxima × C. moschata rootstocks. Despite sucrose accumulation throughout storage at the expense of fructose and glucose, total soluble carbohydrates and soluble solids content declined. Lycopene content peaked 7 days postharvest and intensity of flesh color increased concomitantly; yellowing of flesh was detected at 14 days. Rootstocks reduced soluble solids content only in the second year of experiments by 0.8–1.0°Brix. Rootstocks improved postharvest flesh firmness and lycopene content and enhanced flesh color. Rind was minimally thickened by rootstocks and declined with storage. Grafting diploid cultivars on interspecific rootstocks improved fruit quality and storability. Potential reduction in soluble solids content in response to grafting is limited and not detrimental to fruit quality. PRACTICAL APPLICATIONS: Grafting on disease‐resistant rootstock has become an imperative for intensive watermelon production since chlorofluorocarbon‐based soil fumigants were banned from use. Accordingly, most information on the effects of grafting on watermelon fruit quality derives from rootstock selection studies with emphasis on disease resistance and field performance. However, impaired fruit quality, notably low flesh firmness, constitutes a common problem for the commercial summer crop of field‐cultivated watermelon with blame commonly placed on grafting. Moreover, watermelons worldwide are handled postharvest under adverse nonrefrigerated conditions. There remains, however, a paucity of information on the effects of grafting on watermelon postharvest performance. The main objective of this work was to assess the impact of cucurbit hybrid rootstocks, which constitute a major class of disease‐resistant commercial rootstocks, on quality and postharvest performance of watermelon. The results could be applicable to improve the quality and postharvest handling of the watermelon fruit.