Differences between the olive fruit and leaf abscission zones enable development of a selective abscission compound

The table olive (Olea europaea L.) is a widely produced olive product. Table olives are still harvested by hand. The low efficiency of hand harvesting and the rise in the costs of labor put this crop in a delicate situation. A selective abscission compound is considered crucial for the adoption of table olive mechanical harvesting. We studied the anatomical as well as the molecular differences between the olive fruit and leaf abscission zones. We found that the typical anatomical characteristics of the abscission zone, such as small cells with less pectin compared with neighboring cells, exist in the leaf but not in the fruit abscission zone. Transcriptomic analysis of the various abscission zones revealed induction of genes involved in oxidation stress specifically in the leaf abscission zone. We then found that reactive oxygen species mediated abscission as a response to exogenous ethylene in the leaf but not the fruit abscission zone. Hence, adding antioxidants such as ascorbic acid or butyric acid to the abscission compound enhanced fruit but not leaf abscission. Our findings suggest that farmers should use a differential agent to give decreased detachment force of fruits only and therefore enable mechanical harvesting of table olive.