Responses of Commercial Olive Cultivars (Olea europaea L.) to Cold Stress Using Electrolyte Leakage Method and Measuring Total Soluble Carbohydrate

Identification and characterization of tolerant and susceptible cultivars of crop plants to cold stress is important. In this regard, in present research electrolyte leakage and Total Soluble Sugar (TSS) contents in the leaf and bark tissues in ten olive cultivars, namely, Zard, Mari, Fadak87-1, Fadak87-5, Fadak86, Fadak77, Arbequina, Mission, Blady and Coratina were measured to assess their response to cold stress during two consecutive years. Two years-old shoots from five year-old olive trees were collected in summer and winter from a commercial orchard in Qom, Central Iran and exposed to cold treatments of 0, -4, -8, -12, -16 and -20°C for 24 hours. Then LT50 was measured by electrolyte leakage. A considerable increase in cold-hardiness was observed with decreasing temperature. Leaf and bark tissues exhibited more tolerance in winter than summer and bark tissue had more tolerance than leaf in both seasons. Also TSS contents in leaf and bark tissues were greater in winter than summer and in all studied cultivars bark tissue had greater TSS content than the leaf. Results showed that cold-hardy cultivars, Zard, Arbequina and Fadak87-5 (with tolerance thresholds of -17.34°C, -17.5°C and -17.99°C, respectively) had greater TSS contents in tissues in summer and winter compared to susceptible cultivars, Coratina and Mari (with tolerance thresholds of -7.18°C and -9.13°C respectively). Although the precise mechanism in response to cold stress has not been characterized in olive tree, it can be concluded from this experiment, that the tissue TSS content is closely associated with resistance to cold stress in this tree species

Investigation of the Optimal Harvesting Time in Some Iranian and Mediterranean Olive Cultivars Based on Their Oil Content and Fatty Acid Compositions

Harvest time, in olive, is an important key to achieve high quality and quantity of oil with a desired and balanced fatty acid (high oleic acid and low palmitic and linoleic acid) composition. Appropriate harvesting time varies in different locations depending on climatic and agronomic situations and identifying the right time for harvesting may bring about a high quality oil. Thus, the current study was carried out to determine the best harvesting time for two Iranian (Mari and Shenge) and two foreign (Kroniki and Arbequina) cultivars in the region of Tarom, Zanjan, (north of Iran). The results obtained indicated that palmitic, oleic and stearic acid contents decreased and linoleic and palmitic acid contents increased with the progress of ripening. In addition, oil percentage increased with the progress of fruit growth and development. Based on the amount of desired fatty acids, the best harvesting time for the Mari, Kroniki and Arbeqina cultivars, was 180 days after full bloom. It was revealed that the cultivar Shenge is not suitable for oil extraction, due to the low percentage of oleic acids. Therefore, Shenge could be cultivated for producing olive cans rather than olive oil and the best harvesting time for Shenge is 120 days after full bloom