Abstract Drought is recognized as one of the most important and common environmental stresses that take place in many environments, including the arid and semi-arid areas all around the world. The present study attempted to compare the reaction of two grape cultivars (‘Yaghuti’ grape as the drought tolerant cultivar and ‘Bidanesefid’ grape as the drought sensitive cultivar) to drought stress, and investigate the dominant physiological and biochemical factors of each cultivar under water stress and no-stress (control) conditions. For this purpose, a 4× 2 factorial test was performed in a completely randomized design with six repetitions in green house conditions. Experimental factors including drought stress at four levels of control, 6, 12 and 18 days of drought stress and two grape cultivars: ‘Yaghuti’ and ‘Bidanesefid’ were applied. Relative water content (RWC), total soluble protein content (TSP) and chlorophyll content of the two cultivars decreased with increasing water stress duration. Under drought stress, ‘Yaghuti’ showed a lower decrease in RWC and TSP than ‘Bidanesefid’. Abscisic acid (ABA) content increased in plants under 12 and 18 days of drought stress in comparison to control plants. By increasing the days of stress, proline and total soluble sugar (TSS) content of the ‘Yaghuti’ and ‘Bidanesefid’ increased. Maximum values for proline and TSS content were recorded in 18-day water-stressed plants. In general, our results showed that the two cultivars were not equally affected and that the ‘Yaghuti’ has a higher ability to survive under the same drought stress conditions.
