Physiological responses and fruit quality of four peach cultivars under sustained and cyclic deficit irrigation in center-west of Tunisia

In arid and semi-arid regions, the research and application of new irrigation techniques that economize water without altering tree performance and fruit quality is a challenge. The aim of this study was to investigate the effect of two different deficit irrigation strategies on tree physiology and fruit quality of four Prunus persica cultivars: two early-ripening cultivars (Flordastar and Early Maycrest), a mid-season cultivar (Rubirich), and a late-ripening cultivar (O'Henry). During two consecutive seasons (2016 and 2017), three different irrigation treatments were established: i) Full Irrigation (FI; 100% ET c ), ii) Sustained Deficit Irrigation (SDI; 50% ET c ) and iii) Cyclic Deficit Irrigation (CDI; trees irrigated at 100% field capacity whenever the soil moisture dropped to 50% field capacity). Tree water status, gas exchange, yield, fruit pomology and the concentrations of the main sugars and organic acids were determined. Deficit irrigation decreased net photosynthesis rate, stomatal conductance and transpiration rate while it improved instantaneous water use efficiency (WUEins). In O'Henry cultivar, WUEins increased from 3.21 μ mol mmol –1 in FI to 7.04 μmol mmol –1 in CDI during harvest. Deficit irrigation significantly reduced shoot growth in the four cultivars. Furthermore, SDI decreased the yield significantly (from 41 to 26.3 kg in O'Henry cultivar during 2016), fruit size and weight while CDI increased soluble solids and sugar contents and decreased titratable acidity. The total sugar content increased significantly under deficit irrigation in all cultivars studied. In conclusion, CDI seems to be the best strategy in semi-arid regions, since it can save water and improve fruit quality parameters.