Evaluation response of three apple rootstocks to drought stress in vitro

Water deficit is one of the most important environmental factors that limit crop productivity. Therefore, the need for evaluation of crop tolerance to drought has become urgent. It has been reported that drought resistance of rootstocks is conferred to scions. This study evaluated the response of three apple rootstocks Gami Almasi, MM106 and MM111 to drought stress in in vitro conditions. This experiment was carried out as a factorial experiment based on completely randomized design (CRD) with three replications. Water stress induced by the incorporation of 0, 1, 2 and 4 % polyethylene glycol (PEG-6000) into the Murashige and Skoog medium was applied for 6 weeks. Results showed PEG-induced drought stress reduced growth parameters (length of shoot and root, fresh weight of shoot and root), chlorophyll index and promoted other biochemical parameters (content of proline and soluble sugar and protein and Catalase and Guaiacol peroxidase enzyme activity), but had no significant effect on the shoot diameter. The lowest length of shoot and root, fresh weight of shoot and root and chlorophyll index was observed for MM106 rootstock in 4% PEG treatment and the highest proline, soluble sugars and Catalase were in Gami Almasi rootstock in 4% PEG treatment. According to the results, the Gami Almasi is a resistant rootstock to drought stress.