Frost Tolerances of Turkish Olive (Olea europaea L.) Cultivars

The motherland of the olive is considered as east of the Mediterranean Basin. Turkey is partly located within this basin having a rich source of biodiversity. Olive growing in Turkey is carried out in the Aegean, Marmara, Mediterranean, Southeastern Anatolia and Black Sea Regions. Climatic factors determine the cultivation limits of olive which is not very selective in terms of soil demand. In regions where olives are grown, the Mediterranean climate prevails. Winters are warm and rainy in the region, while summers are hot and dry. On the other hand, severe cold damage in some years can cause significant damage especially in the inner parts of Aegean, Marmara and Black Sea Regions. As a matter of fact, it is known that 31.8% of olive plantations in Turkey are exposed to occasional frost damage. This situation has revealed the necessity of determining the varieties with high frost tolerance and determining the suitable varieties for the regions where cold damage may occur. In the study, 40 registered olive cultivars in “Kemalpaşa Olive Germplasm Bank" in Bornova Olive Research Institute, in İzmir were screened in terms of frost tolerance. To evaluate the frost tolerance (LT50) of cultivars, as estimated by ion leakage (electrical conductivity), leaf samples taken in six different periods over two years were exposed to temperatures at +4 °C (control), -2 °C, -5°C, -8 °C, -11°C, -14 °C, -17 °C and -20 °C. In conclusion; it has been determined that frost tolerance of olive varieties revealed significant variability both genetically and seasonally. Butko, Memeli, Otur, Gemlik, Sinop No 5, Yün Çelebi, Kara Yaprak, Satı and Sarı Ulak were determined as cultivars that were more tolerant of frost. Sinop No 1, Marantelli, Ayvalık, Görvele, Çakır, Samsun Tuzlamalık, Erkence, Saurani, Eşek Zeytini (Tekirdağ), Kan Çelebi, İzmir Sofralık, Çilli, Samsun Yağlık, Domat, Eşek Zeytini (Ödemiş), Saçaklı Otur, Sinop No 4, Memecik, Nizip Yağlık, Tekirdağ Çizmelik and Patos were found to be moderately tolerant cultivars while Edincik, Sinop No 6, Çekişte, Mavi, Kiraz, Kilis Yağlık, Çelebi (İznik), Trabzon Yağlık, Uslu and Girit olive cultivars were grouped as cultivars having low tolerance to frost. In addition, data showed that cold acclimation in the olive is quite important, and exposure to low temperatures for a certain period of time has significantly increased the frost tolerance. However, this condition was not stable and could rapidly become reversed when temperature reached to the point at which adapdation did not ensure.