Determination of cold hardiness of some Turkish red pine (Pinus brutia Ten.) provenances in Ankara and Antalya provenance trials

Turkish red pine (Pinus brutia) is the most important tree species for afforestation in Turkey due to its drought tolerance and rapid growth. However, its distribution is highly limited in arid-cold regions and high elevation areas due to its sensitivity to frost. This study aimed to evaluate frost tolerance of some Turkish red pine origins sampled from provenance trial areas located its natural distribution area and outside of its natural distribution area (Antalya and Ankara). One year-old twigs of Pinus brutia were sampled from provenance trials in Antalya and Ankara. The experiment was a completely randomized parcel design where the frost test temperatures were the treatments. The twigs were subjected to cold temperatures of -5, -10, -12.5, -15, -17.5, -20, -22.5, -25, -30 and -40 0C, and control groups were not subjected to any of low temperatures. After freezing tests, electrical conductivity of the twigs was measured and values were converted to relative damage index (It). Results showed that damages of cell membranes start between -15 and -17.5 0C, while lethal damage occurred at -20 0C at the end of January. Significant variations were found between cold hardiness of origins. Samsun-Bafra (BAF) and Burdur-Gölhisar (GOL) origins were more tolerant to frost compared to those from Antalya provenance trial. Similarly, Burdur-Gölhisar (GOL), Antalya-Kaş (KAS) and Cyprus-Güzelyurt (KIB) origins were more tolerant compared to those from Ankara provenance trials. Mersin-Gülnar (GUL), Antalya-Kaş (KAS), Kıbrıs-Güzelyurt (KIB) and Mersin-Anamur (ANA) origins sampled from Ankara provenance trial had greater frost resistance to frost than the same origins sampled from Antalya. The reason for increased frost tolerance of the origins from Ankara could be attributed to their greater phenotypic plasticity.