Heat tolerance in olive

Heat resistance in shoots and leaves of 10 olive (Olea europaea L.) cultivars was assessed by two different methods. Stem impedance analysis and electrolyte leakage of leaves and shoots were evaluated to determine which method is more reliable for estimating heat injury in olive. A significant decrease in DZratio and increase in electrolyte leakage was found in all genotypes after heat treatment. Results from the two methods showed that both methods were able to detect heat injury in olive. However, electrolyte leakage seemed to work more effectively detecting bigger differences among the heat tolerance of the cultivars tested. It would appear from the present study that shoots are more resistant than leaves to heat injury. On average, leaves and shoots are injured at temperatures around 48 and 50°C, respectively. The lethal temperatures allowed to share out the cultivars in four groups with different tolerance to heat stress. The heat response of these genotypes has been analysed in detail and the limits of artificial heating tests are discussed.