Effect of the exogenous application of abscisic acid (ABA) at fruit set and at veraison on cell ripeness of olives Olea europaea L. and the extractability of phenolic compounds in virgin olive oil

Background: The effect of the exogenous application of abscisic acid (ABA) at the fruit set and veraison on the cell maturity of the olive Olea europaea L. and on the extractability of phenolic compounds (PC) in the virgin oil olive was studied. Methods: The ABA was sprayed on olive trees of the Moroccan Picholine variety at a concentration of 10(-3) mg/l, some olive trees are treated at fruit set stage and other olive trees are treated at veraison stage. The effects of these treatments were evaluated by fruit yield and determination of the date of veraison and ripening period of the olives. The extractability of olive oil and diffusion of PC in the latter as well as the weakening of the parietal structures are also estimated. Results and discussion: The application of ABA at fruit set causes a decrease in the production of fruit about 50% and precocity of ripening estimated 45 days. At this stage, comparing with the control in the same period, there was a significant accumulation of fat in olives, an increase in oil extractability and a significant improvement in the diffusion of PC in oils. The treatment of the olives by the ABA at veraison has no effect on yield. However, we observe physiological and biochemical changes to be identical during the treatment by ABA at veraison but smaller than that at fruit set.