Relative Water Content, Proline, and Antioxidant Enzymes in Leaves of Long Shelf-Life Tomatoes under Drought Stress and Rewatering

Some physiological, oxidative, and antioxidant enzymatic patterns were assessed in plantsof three local Sicilian landraces of long shelf-life tomatoes ('Custonaci', 'Salina', and 'Vulcano'), ascompared to the commercial tomato hybrid 'Faino' (control). Three water treatments were consideredin open-field: DRY (no irrigation); IRR (long-season full irrigation); REW (drought/rewatering cycles).During the growing season, soil water deficit (SWD) was estimated, and relative water content (RWC),specific leaf area (SLA), proline and malondialdehyde (MDA) content, and glutathione peroxidase(GPX), catalase (CAT), and superoxide dismutase (SOD) activities were measured in leaves. Differentlyfrom control, RWC in local landraces exhibited a similar pattern in REW and DRY, indicating a lowcapacity to re-hydrate after rewatering. Positive correlation of proline content vs. SWD in all locallandraces highlights an osmotic adjustment occurring in these tomatoes in response to limited soil watercontent. Long shelf-life tomatoes suffered minor oxidative stress due to severe soil water deficit, asrevealed by the lower levels of MDA with respect to the control. Significant correlation of CAT vs. SWDfor all tomatoes indicates that this antioxidant enzyme, among those analyzed, may be considered as abiomarker for a water stress condition more than for oxidative stress due to water deficit.