Response of some watermelon accessions to water deficiency stress induced by poly ethylene glycol

In order to study the response of five watermelon accessions (TN.93.765, TN.93.469, TN.93.485, TN.93.425 and TN.93.330) to drought stress an experiment was conducted as factorial experiment in Randomized Completely Block Design with three replications. This research were investigated in hydroponic system with four levels of osmotic potential induced by poly ethylene glycol 6000 (PEG) including 0 as control, -0.4, -0.8 and -1.2 MPa. Based on results among accessions remarkable differences were observed. Accessions of TN.93.765 and TN.93.485 revealed the lowest reduction in fresh and dry weight and leaf area and also the highest amount of photosynthetic pigments at severe stress condition (-1.2 Mpa). Amount of chlorophyll and carotenoid pigments gradually increased with increasing osmotic potential up to -0.8Mpa but reduced at -1.2 Mpa. Accessions of TN.93.765 from Isfahan and TN.93.485 from Khorasan obtained maximum amount of proline, total phenolic compound and antioxidant capacity in severe stress condition. Based on the results we could demonstrate that these accessions were more tolerable to drought stress in comparison with others.