Enhancing saffron (Crocus sativus L.) cormlet production under high-temperature stress: Integration of biological and...

Saffron (Crocus sativus L.) cultivation faces increasing challenges from climate change and declining yields. Optimal corm development occurs at 15/6 °C day/night temperatures. However, climate change is forcing cultivation under higher temperature regimes.This study investigated the effects of Trichoderma harzianum Bi, nano-TiO₂, and magnetic field treatments on saffron cormlet production under high-temperature greenhouse conditions (25/15 °C day/night, exceeding optimal temperatures by 10 °C), representing increasingly common stress conditions in traditional growing regions. While controlled environment production offers potential solutions, the combined effects of biological and physical treatments for mitigating high-temperature stress remain unexplored.

A factorial experiment examined T. harzianum Bi-enriched medium (0, 100% v/v), nano-TiO₂ (0, 250, 500 μl l^-1), and magnetic field exposure (0, 60 militesla, 30-min constant exposure) effects on uniform-sized saffron corms (13 ± 0.5 g) grown in cocopeat-perlite medium (3:1 v/v). Analysis included cormlet production parameters and comprehensive metabolic profiling of key compounds including carbohydrates, amino acids, and organic acids.

Combined T. harzianum and 250 μl l^-1 nano-TiO₂ treatment significantly enhanced cormlet production, increasing individual cormlet weight by 68.9% (from 9.0 ± 0.2 to 15.2 ± 0.3 g/cormlet, p < 0.05) and improving key metabolites: starch (37.6% increase to 255.2 ± 20.4 mg g^-1 FW), GABA (159.6% increase to 1.35 ± 0.11 μmol g^-1 FW), and myoinositol (111.1% increase to 0.95 ± 0.08 mg g^-1 FW). Magnetic field exposure increased cormlet numbers but reduced individual weights by 20%. Metabolomic analysis revealed coordinated enhancement of carbohydrate metabolism and stress-response pathways.

For commercial production, we recommend applying combined T. harzianum (100% v/v medium enrichment) with 250 μl l^-1 nano-TiO₂ treatment under controlled greenhouse conditions (25/15 °C Day/night). This protocol consistently produces larger, more vigorous cormlets with enhanced metabolic profiles, though magnetic field applications require further optimization. These findings provide immediate practical strategies for addressing cultivation challenges under increasing temperature stress conditions, particularly relevant for commercial greenhouse production systems.