The study of some native and exotic olive cultivars and genotypes in terms of morphological diversity, oil quality and fatty acid composition

Iran is renowned as one of the olive origins in the world; therefore, characterizing and conserving the existing genotypes compared to exotic cultivars and organizing these genotypes are of critical importance. One of the most important factors in successful cultivation of olive trees is the identification and selection of suitable cultivars for each geographic region to produce oil with appropriate quantity and quality. This study was conducted to evaluate the genetic diversity of 12 native and exotic olive cultivars using morphological traits and to select the compatible cultivars for Gorgan region. The study was carried out using a completely randomized design with three replications, in which the quantitative and qualitative morphological characteristics were measured according to the procedure of International Olive Oil Council. The maturity index of fruit was measured according to a standard method suggested for olive. The oil was extracted using soxhlet method and the percentage of oil was recorded in both dry and fresh matters. For quality assessment of the oil, the oil also extracted using centrifugation method. The results suggested that there was a huge diversity among the selected cultivars and genotypes based on morphological characteristics. Cluster analysis could be utilized as a powerful tool to screen and classify the genotypes. The cluster analysis based on the morphological quantitative data, showed that the cultivars were classified in three groups and each group contain the genetically similar genotypes which were different from the genotypes in other groups. There were also several subclusters suggesting considerable diversity within each group. There were some significant correlations among the measured characteristics. For instance there was a positive correlation between the fruit weight and the leaf length and width. The results showed that the cultivars had considerable variation in the oil percent in dry and fresh weight. In the next stage, the oil quality of four selected oil cultivars including Zard, Balady, Leccino and Arbequina were analyzed. The highest amount of chlorophyll (1.16 mg/kg) and carotenoid (0.718 mg/kg) were related to Leccino. The highest amount of peroxide value (11.33 meq o2/kg oil) was also in Leccino, while the lowest one (7.8 meq o2/kg oil) was observed in Zard. The highest amount of spectrophotometric index K232 was in Arbequina and no significant difference was observed among the cultivars in amount of K270. There were not any significant differences among the cultivars in acidity. Analysis of fatty acids indicated that Balady had the highest percent of oleic and linolenic acid (78.06% and 0.513%, respectively). The highest percent of palmitic acid was in Zard (19.1%) and the percent of linoleic and estearic acids were not significantly different. According to the results, Balady cultivar showed higher oil quantity and quality compared to other three cultivars and is suitable for cultivating in the region.