Evaluation of the Effect of Native Cultivars as a Rootstock on the Tolerance to Drought Stress in ‘Crimson Sweet’ Watermelon

The use of drought-tolerant rootstocks, such as seeded and rainfed watermelons, and pumpkins, is an effective solution for increasing tolerance to drought stress in watermelons. For this purpose, this experiment was conducted in a greenhouse to evaluate the effects of irrigation treatment at three levels (1-0.8; 0.6 -0.8; and 0.3-0.6 FC) and rootstock type at five levels (control, three rootstocks of rainfed and seeded watermelons including Sabzevar, Khajahe and Ashtian and one rootstock of pumpkin: Shintoza) on physiological and biochemical parameters in watermelon Crimson Sweet Super Dragon F1. The results showed that the number of leaf stomata in grafted and non-grafted plants decreased with the increase of dryness levels, and the grafted plants on Shintoza rootstock had a higher stomatal density. Drought stress caused a significant decrease in chlorophyll index and leaf relative water content and increased electrolyte leakage in studied watermelons. The total antioxidant capacity and the activity of catalase and peroxidase enzymes increased as a result of drought stress, but this increase was greater in grafted plants on Shintoza and Sabzevar rootstocks than in plants grafted on Ashtian and Khajahe rootstocks as well as watermelons.. Watermelons grafted on Sabzevar and Shintoza rootstocks produced the highest content, while non-grafted and grafted watermelons on Ashtian rootstocks produced the lowest content of leaf phenolic compounds Potassium and phosphorus levels in plants with normal irrigation were higher than plants under stress. As a result, yield and vegetative growth traits were significantly affected by irrigation and transplanting treatments.