A Comparative Analysis of Drought Tolerance Mechanisms in Triticum araraticum Jakubz. and Modern Bread Wheat (Triticum aestivum L.) Cultivars

Wild wheat relatives are promising sources of drought tolerance that demonstrate adaptive mechanisms not found in modern wheat cultivars. This study investigated and compared the drought tolerance mechanisms in Triticum araraticum genotypes, a relatively unexplored species, with those of modern Triticum aestivum cultivars. Osmotic regulation, antioxidants, and gas exchange traits were evaluated under well-watered and drought treatments. Overall, high-yielding bread wheat cultivars exhibited a higher photosynthetic rate, instantaneous water use efficiency, and greater antioxidant activity, with a few exceptions compared with T. araraticum under the well-watered treatment. Drought stress significantly reduced stomatal conductance, internal CO₂ concentration and photosystem II efficiency. It induced a significant increase in the content of proline, total soluble sugars and most enzymes involved in the ascorbate–glutathione cycle, except for ascorbate peroxidase and ascorbate oxidase, which remained unresponsive. T. araraticum genotypes demonstrated a more pronounced drought response with distinct antioxidant tolerance mechanisms compared with modern T. aestivum cultivars. Specifically, in T. araraticum, the increase in the redox state of glutathione, driven by enhanced glutathione reductase activity, was higher than that of ascorbate under drought stress. By contrast, T. aestivum maintained increased activity of guaiacol peroxidase and enhanced ascorbate redox state through dehydroascorbate reductase. This study provides valuable insights into the unique antioxidant and osmotic regulator of T. araraticum that differ from those of modern bread wheat cultivars. Its findings can inform future wheat improvement programs aimed at developing climate-resilient wheat cultivars for sustainable agricultural systems.