The objective of this research was to investigate the effects of deficit irrigation on physiological and agronomic terms of eggplant to maximize the Water Use Efficiency (WUE) without affecting the final yield and fruit quality parameters under arid environment. Therefore, two field experiments were conducted at two different sites: Ghor Al-Safi, Jordan Valley and Sail Al-Karak, Karak Valley, Karak Province, Jordan, using a common eggplant cultivar (Classic) using five irrigation levels: 20,

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... 60, 80, and 100% based on field capacity. The most stressful Deficit Irrigation (DI) treatments (40 and 20%) resulted in significant effects on leaf area, leaf relative water content, leaf water potential and leaf mineral content. Biochemical parameters also showed an increase in proline and a decrease in chlorophyll content under water deficit conditions. Fruit weight and total yield decreased with DI. The control (100% irrigation treatment) plants revealed higher nutrient contents than the water-stressed plants. The fruit TSS and titratable acidity were increased at both sites as the irrigation regime decreased from 100 to 20%. Fruit nutrient content decreased with increasing water deficit. However, the differences were not significant between the control (100% irrigation treatment) and the 80% irrigation treatment. The 80% treatment showed high water use efficiency with relatively small effects on plant growth performance compared with the control. As a result, DI level at 80% can be utilized to increase WUE without a significant effect on crop growth performance.