Influence of Fruit Load and Water Deficit on Olive Fruit Phenolic Profiling and Yield

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Abstract
High-density olive groves, despite their interesting production potential, have several limitations, including their high fruit load and irrigation requirements. This study aimed to evaluate the effects of fruit load and deficit irrigation on oil yield, fruit quality, and olive chemical composition in a high-density olive grove (cv Sikitita). Our main hypothesis was that primary metabolism, as influenced by crop load and stress, could modify the accumulation of different phenolic classes. Different fruit loads were generated through flower thinning (66%, 50%, 33%, 0%), and two deficit irrigation treatments (−60%, −75%) were compared to the well-watered control (920 m3/ha). Thinning treatments had a limited effect on oil yield; on the other hand, deficit irrigation caused considerably less oil accumulation in the fruit on all sampling dates. Thinning 66% and deficit irrigation 75% were considered with the control for untargeted metabolomic analysis, including three sampling dates. A total of 233 distinct phenolic compounds were annotated. Multivariate HCA results indicated that harvest time had an impact on the phenolic profile of olive fruits, obtaining two separated clusters that grouped t1 and t2 together and apart from t3, which clustered independently. Regarding agronomic techniques, they played a differential role in the phenolic profile (supervised OPLS-DA). Fruit load mostly affected flavonoid glycosides. In contrast, the phenolic response to deficit irrigation was more heterogeneous, with phenolic acids (35%), flavonoids (25%), LMW, and other phenols (25%).

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