The influences of grafting treatments (6001 and Star rootstocks in addition to, check nongrafted transplants) and some foliar spray treatments (potassium silicate at rate 4 and 5 ml/L, calcium at rate 1 and 2 ml/L and check) on growth, yield and fruit quality of watermelon cv. Aswan F1 were investigated. The experiment was conducted in Baloza Research Station, Desert Research Center, at North Sinai Governorate during the two successive growing seasons of 2016 and 2017. The results indicated that plants sprayed with potassium silicate at a rate 5 ml/L or grafted onto Star rootstock recorded the highest significant values on transplant stand (success) percentage, vegetative growth characteristics (plant length, fresh and dry weight), yield and its components (fruit weight, fruit size, rind and flesh thickness and total yield), while the lowest values were observed in check nongrafted plants. Meanwhile, grafting had reducing effect on fruit quality, where the highest values of total soluble solids and total sugars were found in the fruits of nongrafted plants. The application of 5 ml/L potassium silicate gave the best significant values of TSS and total sugars compared with check treatment during the two studied seasons.

Pots experiment was conducted in the experimental farm of Agricultural Botany Department, Faculty of Agriculture, Ain Shams Univ. during the seasons of 2015 and 2016 to investigate the effect of grafting on salt tolerance of watermelon plants. Watermelon (Citrullus lanatus, Hybrid F1) Aswan1 was grafted onto the rootstock of Flexifort pumpkin (Cucurbita maxima x C. moschata) and irrigated with four different concentrations of NaCl (0.0, 2000, 4000, 6000 ppm). Two samples were taken at  20 and 40 days after planting (DAP). Plant height, leaf numbers and area, branches number, root length, and shoot and root fresh and dry weights were negitavly affected by salinity in ungrafted plants and this effect was directly proportional to NaCl concentrations. On the contrary, grafting positively affected the aforementioned parameters and minimized the harmful effect of salinity. Furthermore, grafted plants showed higher growth vigor comparing with ungrafted control plants or plants received the same treatment of NaCl and these effects were mostly siginificant. An increase in membrane permeability (MP) was detected at 20 and 40 DAP by application of different levels of NaCl salinity and this effect was positively correlated with NaCl concentration. Grafted plants showed decreasing in MP with 12.7% higher LRWC than ungrafted plants. Under 2000, 4000, 6000 NaCl ppm salinity levels, the values of salt injury index recorded 15.1, 26.5 and 37.5 in ungrafted plants at 20 DAP comparing with 0.0, 6.9 and 12.9 in grafted ones.