Assessment of Cold Stress Tolerance in the Leaves of Some Olive (Olea europaea L.) Cultivars

Severe cold is one of the most important limiting factors for olive production. This research aimed to evaluating and selecting cold-tolerant olive cultivars. Therfore, six olive cultivars including; Grossane, Abusatl, Koroneiki, Chavar, Siab and Kolafaraj were evaluated under five cold treatments (Control, -9°C, -11°C, -13°C and -15°C). Electrolyte leakage, leaf thickness and relative water, nitrogen, calcium, potassium, total carbohydrate, oleic and linoleic acids contents of the leaves of olive cultivars were measured. The results indicated that the lowest leaf thickness related to cv. Koroneiki with average of 0.42 mm. The highest total carbohydrate was in the leaves of Grossane (4.83%) and the lowest in Koroneiki (2.20%). The cultivar × cold treatment interaction effect showed that in the -9°C, the highest changes in electrolyte leakage, as compared to the control temperature, was in cv. Siab (53.26%) and Koroneiki (48.59%). At the -11°C, the highest electrolyte leakage related to Kolafaraj (73.39%). There was significant difference between cold treatments for electrolyte leakage. As the temperature decreased to -15°C, electrolyte leakage increased. Mean comparison showed that cv. Abusatl (60.0%) and Grossane (60.86%) had the lowest electrolyte leakage. Correlation coefficient between oleic acid and linoleic acid contents was negative and significant (r = -0.490*). Relative water content had positive and significant correlation coffeieceint (r = 0.533*) with leaf potassium content. Leaf thickness had positive and highly significant correlation with oleic acid (r = 0.878**), and significan with linoleic acid (r = 0.545*). Correlation coefficient between total carbohydrate and linoleic acid was positive and significant (r = 0.804**). Based on the results of this research cv. Abusatl and Grossane were cold tolerant, and cv. Koroneiki, cv. Siab and cv. Kolafaraj were cold sensitive.