Growth, yield and physiological responses of watermelon cv. Charleston Gray grafted on bitter apple (Citrullus colocynthis L.) rootstock under deficit irrigation stress

In order to study the effect of deficit irrigation stress on growth, yield and physiological traits of watermelon (Citrullus lanatus cv. Charleston Gray), an experiment was carried out in a split plot based on randomized complete block design with three replicates in university of Zanjan. Treatments consisted of three irrigation levels (100%, 70% and 50% Crop Evapotranspiration (ETc)) and grafting (plants grafted on bitter apple and ungrafted plants). Results showed that deficit irrigation stress significantly decreasedgrowth, yield and water use efficiency (WUE) and increased electrolyte leakage and proline content. The highest value of fruit yield and WUE were obtained in ungrafted and grafted plants under irrigation 100% ETc. The maximum soluble solid content was recorded at grafted plant under deficit irrigation 50% ETc. The highest leaf area, plant length, fruit firmness and RWC were obtained in ungrafted plants under irrigation 100% ETc. The maximum POX activity was observed in grafted plants under deficit irrigation 50% ETc. Bitter apple rootstock decreased calcium concentration under irrigation 100% and 70% ETc and increased blossom end rot (BER), but by increasing deficit irrigation stress, calcium concentration in ungrafted plants was decreased and BER was increased. According to the results, grafting on bitter apple rootstock had no positive effects.