Journal of Plant Process and Function

Drought stress is the most important environmental factor limiting the growth, yield and quality of crops and horticultural products all over the world. This research was carried out with the aim of investigating and comparing some of the physiological and biochemical responses of two grapevine cultivars differing in drought tolerance, to different levels of water restriction. For this purpose, a factorial experiment was conducted in a completely randomized design with six replications in greenhouse conditions. Drought stress was performed by the method of cut off irrigation in four levels of 0 (control), 6, 12 and 18 days on the two Yaghuti and Bidanesefid cultivars. The results showed that drought stress significantly reduced leaf relative water content in both cultivars. In terms of maximum stress (18 days), the decrease in leaf relative water content was 16.9% for Yaghuti and  21.8% for Bidanesefid cultivar. Under the different periods of drought stress, in the present study, the Yaghuti drought tolerant cultivar showed lower amounts of hydrogen peroxide, malondialdehyde and electrolyte leakage compared to the sensitive cultivar of Bidanesefid. In Yaghuti cultivar, the activity of catalase, peroxidase and superoxide dismutase enzymes in the 18-days drought stress duration, was 2.1, 1.6 and 1.6 times higher than those in Bidanesefid cultivar, respectively. Totally it seems that Yaghuti with its more powerful antioxidant system has more ability for reducing the oxidative damage caused by drought stress, especially in severe stress conditions. In addition to physiological and biochemical studies, molecular experiments with the aim of identifying the genes involved in drought tolerance of this cultivar and other tolerant cultivars, are also very helpful and effective in advancing grape breeding programs.