Olive is a long-living perennial species with a wide geographical distribution, showing a large genetic and phenotypic variation in its growing area. There is an urgent need to uncover how olive phenotypic traits and plasticity can change regardless of the genetic background. A two-year study was conducted, based on the analysis of fruit and oil traits of 113 cultivars from five germplasm collections established in Mediterranean Basin countries and Argentina. Fruit and oil traits plasticity, broad‐sense heritability and genotype by environment interaction were estimated. From variance and heritability analyses, it was shown that fruit fresh weight was mainly under genetic control, whereas oleic/(palmitic + linoleic) acids ratio was regulated by the environment and genotype by environment interaction had the major effect on oil content. Among the studied cultivars, different level of stability was observed, which allowed ranking the cultivars based on their plasticity for oil traits. High thermal amplitude, the difference of low and high year values of temperature, negatively affected the oil content and the oleic acid percentage. Information derived from this work will help to direct the selection of cultivars with the highest global fitness averaged over the environments rather than the highest fitness in each environment separately.

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Different techniques of oil extraction are applied in Jordan, including traditional press, two-and three-phase systems. Results of the study indicated that there is a significant difference in olive oil quality obtained from different pressing systems in terms of free acidity, ultraviolet absorption, peroxide value, polyphenol content, organoleptic assessment and overall quality index. Olive oils obtained from the two-phase mills were classified as extra virgin olive oil. While, olive oils obtained from the three-phase mill were ranged from extra to ordinary virgin olive oil. In the contrary olive oils obtained from the three conventional mills were classified as lampante virgin olive oil. The two-phase decanters produce high quality olive oils with higher contents of total polyphenols which makes them more resistant to oxidation during storage. These decanters, also having an advantage of saving on wastewater disposal costs because they produce only a small amount of such waste.