Characterization of the Differential Tolerance of Two Triticum durum Cultivars to Short-Term Cadmium-Induced Stress

Cadmium (Cd) is a toxic heavy metal that impairs plant growth and induces oxidative stress. In this study, we compared the physiological, biochemical, and molecular responses of two durum wheat (<i>Triticum turgidum</i> ssp. <i>durum</i>) cultivars, Razek and Chili, to Cd stress. Seedlings were exposed to 0, 5, and 50 µM Cd (Cd²⁺; supplied as CdCl₂) under controlled hydroponic and Petri assay conditions. Cd reduced radicle elongation, biomass accumulation, and water uptake in both cultivars, but the relative inhibition of growth was lower in Razek than in Chili, indicating a better capacity to maintain growth under Cd stress. This was accompanied by milder oxidative stress symptoms and more stable antioxidant enzyme activity, particularly for catalase (CAT) and ascorbate peroxidase (APX). Gene expression analyses revealed that Razek maintained a higher expression of antioxidant and stress-related genes under acute Cd stress, while Chili exhibited pronounced downregulation. Histochemical analyses showed increased H₂O₂ accumulation and lignin deposition in Chili roots, suggesting a stronger stress response. Notably, Chili also showed a sharp depletion of reduced glutathione (GSH) under high Cd concentrations, with limited upregulation of GSH synthesis and phytochelatin-related genes. Together, these findings indicate that Razek activates more efficient detoxification, redox regulation, and hormonal signaling pathways under Cd stress, indicating its potential suitability for cultivation in slightly Cd-contaminated soils.