Cultivar-specific responses of young olive trees to water deficit: impacts on physiology, leaf anatomy, and fruit quality in 'Arbequina', 'Leccio del Corno' and ‘Maurino’

: Understanding cultivar-specific responses to water deficit is crucial for sustainable olive production under water-limited conditions. This study investigated the physiological, anatomical, and fruit quality responses of three olive cultivars: 'Arbequina' (a widely used cultivar in intensive systems), and the Italian autochthonous cultivars 'Leccio del Corno' and 'Maurino'. Three-year-old potted plants were subjected to water deficit (WD, 50 % ET) or full irrigation (WW, 100 % ET) during the pith hardening phase. Physiological measurements, including gas exchanges, chlorophyll fluorescence, water relations, and plant hydraulics, were performed at two time points (T1 and T2). Leaf anatomical adjustments and fruit phenolic composition were also evaluated. Under WD, 'Arbequina' maintained high photosynthetic rates but showed higher xylem embolism vulnerability, indicating less conservative water use. 'Leccio del Corno' showed higher intrinsic water use efficiency and lower hydraulic vulnerability, while 'Maurino' exhibited more conservative water use, supported by increased leaf cuticle thickness. Fruit phenolic composition was also cultivar dependent. While 'Arbequina' and 'Leccio del Corno' maintained or increased fruit oleuropein and flavonoids under WD, 'Maurino' showed a decline, suggesting reduced ability to sustain fruit quality. These results highlight significant genotypic variability in drought tolerance, underscoring the importance of selecting cultivars with suitable physiological and anatomical traits for water-scarce environments. 'Arbequina' and 'Leccio del Corno' appear promising for deficit irrigation systems, while 'Maurino' may require full irrigation for optimal performance and quality.