Evaluation of rootstocks for watermelon grafting with reference to plant development, yield and fruit quality

The effect of grafting and post-grafting temperature on the plant development of two watermelon cultivars at transplantation and on subsequent fruit quality was studied. Watermelon cv. Sugar Baby and Crimson Sweet were self-rooted or grafted onto rootstock RS 841 F1 (Cucurbita maxima × C. moschata) or bottlegourd [Lagenaria siceraria f. clavata] (year 1), plus L. siceraria f. pyrotheca (year 2). After grafting, plants were held at 8 oC or 16 oC (minimum) until transplantation (28-29 days), at which stage growth was compared with that of the self-rooted control held under the same conditions. Plants were planted in the field and fruit quality assessed at harvest. At the time of transplantation in year 1, plants at 16 oC were taller and had a higher total fresh weight than those at 8 oC. The grafted plants of both cultivars were taller and had a higher leaf area and fresh weight than the self-rooted plants, irrespective of rootstock. In year 2, the grafted plants of both cultivars had better development (height, leaf area, leaf number, fresh weight) than self-rooted plants. The plants of Crimson Sweet × L. siceraria f. pyrotheca were taller than those of the other two scion-rootstock combinations, irrespective of temperature. Mean fruit weight at harvest was higher in grafted plants than in self-rooted plants, and sugar content varied with scion-rootstock combination. Grafting of watermelon results in better plant growth by the time of transplantation, whereas the scion-rootstock combination affects fruit quality. A minimum temperature of 16 oC is indicated during the post-grafting stage.