Prof. Dr. Hatice Gülen announced that for the first time in Türkiye, all local olive genetic resources have been screened for freezing tolerance, noting that the varieties “Sarı Yaprak,” “Elmacık,” “Butko,” and “Otur” form the most tolerant group against frost.
Olives and olive oil hold significant importance in the cultures and economies of Mediterranean countries such as Türkiye, Greece, Italy, and Spain. Among the major factors affecting olive cultivation is climate change. The Mediterranean climate, with its rainy winters and hot, dry summers, provides the most ideal conditions for olive growing.
However, the increasing frequency and severity of extreme weather events caused by climate change—such as droughts, storms, and floods—have impacted olive cultivation, as in many other crops. Frost is among these critical weather events, reducing both yield and quality in olives and olive oil. Experts warn against growing olives in areas prone to frost, especially during March and April.
Prof. Dr. Hatice Gülen, a faculty member at the Department of Molecular Biology and Genetics, Faculty of Engineering and Natural Sciences at Istinye University, conducted a comprehensive study in collaboration with the Bornova Olive Research Institute under the Ministry of Agriculture and Forestry and TÜBİTAK-MAM to determine the frost tolerance of olive varieties in Türkiye.
90 Registered Olive Varieties Examined
Speaking about the study titled “Determining the Frost Tolerance of Olive Varieties Originating from Türkiye, Developing High Frost-Tolerant Varieties, and Identifying Candidate Genes Responsible for Frost Stress”, Prof. Dr. Gülen stated that the olive tree is a long-lived plant cultivated for both its fruit and oil.
Highlighting the health benefits and economic value of olive products, she explained that they aimed to investigate how olives respond to frost stress. For this purpose, they analyzed 90 registered olive varieties from the Olive Gene Bank in İzmir-Kemalpaşa, part of the Bornova Olive Research Institute.
Gülen emphasized that their work is the first detailed study in Türkiye to screen local olive genetic resources for freezing tolerance and classify varieties based on their cold tolerance:
“For the first time in our country, all olive genetic resources were simultaneously tested in this respect, and significant findings were obtained regarding their frost tolerance levels.”
The research revealed variability in certain genes linked to the plant’s defense mechanisms under frost stress. Sharing the results, Gülen said:
“We found that the resistance of olive varieties to frost shows significant variability both genetically and seasonally. We classified the varieties into five groups, from highest to lowest tolerance. The four varieties—Sarı Yaprak, Elmacık, Butko, and Otur—showed very high tolerance to cold exposure between -18°C and -20°C. Thirteen varieties tolerated cold down to -11°C, which we evaluated as relatively low tolerance. The remaining varieties were grouped between these two extremes.”
Gülen added that the genes DLP, LBR, A-Ind, Zea, STK, and Kir-L, along with their related proteins, play an important role in frost tolerance. The team also developed a DNA-based molecular marker that can be used in breeding programs to improve frost tolerance.
She underlined that the adaptation of olive varieties to cultivation areas will change due to climate change and that the study now makes it possible to recommend suitable varieties for each climate condition.
“In the future, olive varieties can be grown according to new temperature maps resulting from climate change, helping prevent fatal plant damage from harsh conditions and ensuring the preservation of all varieties in gene banks.”
Gülen also noted that a database has been created for recommending varieties based on the critical temperatures of olive-growing regions, and stressed that this research will also enable the development of new varieties through breeding methods that are resilient to changing climate factors, thanks to molecular-level understanding of these factors.
