According to the Greek mythology Athena, the goddess of wisdom, presented the most precious gift to the people in order to name their city after her; the gift was the olive tree and the city was named Athens. The olive tree is symbolizing peace and prosperity, wisdom and longevity. The olive tree is closely related to the Greek history and has played an important role as a symbol and as a commodity. Although domestication of olive most likely occurred in the Middle East about 6,000 years ago, at the Prehistoric museum in Santorini, Greece, the oldest olive leaf fossils found in the Mediterranean (about 60,000 year-old) are on display. Greece has been proposed as primary or a secondary center of domestication. For the last 20 years our group has been studying the olive tree in a number of different aspects including genetic diversity, genomic structure, cytogenetics, active compounds, and photosynthesis. Greece is among the world’s leading olive producing countries (total production in 2014 was 1,780,560 tons – 3rd worldwide producing about 16%). About 90% of the total acreage (938,270 ha) is cultivated with about 20 cultivars either for olive oil or table olives. However, the number of identified cultivars, based on morphological markers and geographical presence, are more than one hundred. In order to find their genetic relationships and the possible duplications, morphological and molecular markers have been used. Based on the structure analysis the olive cultivars were divided into four groups; some cultivars within each group were found to be genetically homogeneous, while others were found to have a high admixture. Data suggested that both sexual and vegetative propagation have contributed to the evolution of the Greek olive germplasm. Furthermore, clustering of olive cultivars was correlated to their primarily usage (table or oil producing) and fruit size. Finally, those olive cultivars that were characterized provided a useful clarification on synonyms and homonyms, facilitating the identification of duplicates. This material is of immense importance due to the fact that regional cultivars have been selected over the centuries for their adaptation to microclimate and soil type. Based on their diversity and cultivated acreage some cultivars were selected for further studies. Leaf CO₂ assimilation rate, stomatal conductance (gs), internal CO₂ concentration (Ci), chlorophyll (a + b) content, specific leaf weight (SLW) and stomatal density were measured during the season, under field conditions, revealing that  ‘Koroneiki’, a drought resistant cultivar, was performing better compared to the rest, maintaining a high CO₂ assimilation rate, even under high vapor pressure deficit. Furthermore, the phenolic profile, the total phenolic content and the antioxidant activity of leaves and drupes were also studied. Differences were observed in the concentration of phenolic compounds depending on the variety in all tissues tested (new season leaves, green and black drupes). The concentration of oleuropein showed high fluctuations both between different tissues within the same variety and between different varieties within the same tissue. As expected, a positive correlation between the antioxidant activity and the total phenolic content was found.

 

 

This abstract was accepted to be presented at the conference entitled “40 Years of Horticulture Education in Cluj-Napoca†Cluj-Napoca, September 27, 2017, being included in ‘Book of Abstracts’ of this special-anniversary event (http://conference.shst.ro). All accepted papers will be published in a special issue of Notulae Botanicae Horti Agrobotanici Cluj-Napoca journal.