Physiological Responses and Antioxidant Enzymes Activity in Some Grapevine Cultivars under Heat Stress Conditions

In recent years, grape growing areas has extended to warm region, therefore, study on grapevine response to heat stress for screening and selection of heat tolerant cultivars is important. Antioxidant systems activity in plants is one of the most important plant adaptation mechanisms to abiotic stresses. This research aimed to determine the response of antioxidant enzymes such as catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and superoxide dismutase (SOD) activities to heat stress in six grapevine cultivars under vineyard conditions. Some physiological traits including; total leaf chlorophyll, chlorophyll a and b contents and chlorophyll fluorescence (Fv/Fm) response were also measured. Results showed that CAT and POD enzymes played criticals roles in the grapevine defense system under high temperature stress. Flame Seedless and Rotabi cultivars had high CAT and POD enzymes activities. Total chlorophyll, chlorophyll a and b concentration were associated to higher Fv/Fm, and were the highest in Flame Seedless followed by Rotabi cultivar. It was concluded that the highest levels of physiological parameters and antioxidant enzymes activities involved in heat stress tolerance in Flame Seedless and Rotabi cultivars, respectively. Similarity between results of this research and previous study under heat stress conditions in which Flame Seedless and Rotabi cultivars had the highest yield showed that physiological traits and antioxidant enzymes activity have the potential for screening grapevine cultivars for heat stress tolerance.