Physiological and Agronomic Benefits of Seed Priming in Durum Wheat Exposed to Tillering and Anthesis Drought

A controlled pot experiment was conducted to evaluate the effects of seed priming on physiological traits, growth, and yield components of four durum wheat (Triticum durum) varieties—Hourani, Umqais, Sham 1, and Maru 1—under drought stress imposed during the tillering and anthesis stages. Four seed treatments were applied prior to sowing: hydropriming with distilled water, osmopriming with polyethylene glycol (PEG), osmopriming with 1.5% calcium chloride (CaCl₂), and an untreated control. Seeds were primed for 12 hours at 24 °C. Drought stress was simulated by withholding irrigation for seven days during each respective stage, and plants exposed to drought stress were compared to well-watered controls. The experimental layout followed a 4 × 4 × 3 factorial design within a completely randomized design (CRD) with three replicates. Under anthesis-stage drought, seed priming significantly improved key physiological parameters, including the transpiration rate (+29%), total chlorophyll content (+1.7%), and relative water content (RWC, +3.5%), relative to the tillering stage. Conversely, drought stress reduced these parameters by 18.6%, 6.5%, and 12.1%, respectively. Osmopriming with PEG led to a 35% higher transpiration rate and 4.9% greater RWC compared to hydropriming during anthesis. In terms of agronomic performance, the PEG and CaCl₂ osmopriming treatments significantly enhanced both growth and yield metrics over hydropriming. Notably, Sham 1 exhibited the highest grain yield increase (82.7%) under PEG priming, while Hourani showed the most severe yield reduction (67.8%) under anthesis-stage drought. In conclusion, seed priming, particularly with PEG or CaCl₂, substantially enhanced durum wheat’s physiological resilience and productivity under drought, with the most pronounced effects observed during anthesis. This suggests that seed priming is a promising strategy for improving drought tolerance in durum wheat cultivated under water-limited conditions.