In this study, two hydroponic experiments were conducted in nutrient solution growth system. Experiments were conducted in growth chamber of Erciyes University, Agricultural Faculty in Kayseri, Turkey. In the first experiment, 10 local Turkish bottle gourd genotypes and two commercial watermelon cultivars were screened under 2 N doses (0.3 mM and 3.0 mM N) in RBD design with three replications for six weeks. In the second experiment, four genotypes (N-efficient: 70-07 and 07-45, N-inefficient: 35-10 and 45-07) were selected and used as rootstock for grafting with N-inefficient watermelon cultivar (Crimson Sweet) under 2 N doses. The grafted N-efficient gourd genotypes (07-45 and 70-07) significantly contributed to growth and biomass production of the N-inefficient watermelon plants as compared to non-grafted control plants and thus showed a higher rootstock potential for watermelon. The N-efficiency of some gourd genotypes was associated with vigor root growth and active root system particularly at low N conditions. These traits could be useful characters to select 'N-efficient' bottle gourd rootstocks for sustainable agriculture in the future.