Irrigation and fruit canopy position modify oil quality of olive trees (cv. Frantoio)

Background: Fruit development and oil quality in Olea europaea L. are strongly influenced by both light and water availability. In this study the simultaneous effects of light environment and irrigation on fruit characteristics and oil quality were studied in a high-density orchard over two consecutive years. Olive fruits were harvested from three canopy positions (intercepting about 64%, 42% and 30% of above canopy radiation) of fully-productive trees subjected to full, deficit or complementary irrigation. Results: Fruits receiving 61-67% of above canopy radiation showed the highest fruit weight, mesocarp oil content and maturation index, whereas those intercepting only 27-33% showed the lowest values. Palmitoleic and linoleic acids increased in oils obtained from fruits exposed to high light levels, whereas oleic acid and the oleic-linoleic acid ratio decreased. Neither canopy position nor irrigation affected the K232 , K270 , ∆K, and lignans concentration in virgin olive oils (VOOs). Total phenols, 3,4-DHPEA-EDA and p-HPEA-EDA increased in VOOs produced from fruits harvested from the top of the canopy, whereas full irrigation decreased total phenols and 3,4-DHPEA-EDA concentrations with respect to the complementary irrigation treatment. Conclusion: Light and water availability are not only crucial for tree productivity, but they also clearly affect olive oil quality.