Unravelling the Multi-Tiered Drought Tolerance in Spelt and Modern Wheat: From Morphology to Grain Nutrition

Drought stress is one of the major limitations to wheat (Triticum aestivum) productivity, which not only affect yield but also change the nutritional quality of grains. In this research, the morpho-physiological, biochemical, and grain nutritional responses of three wheat genotypes, namely WH 1080 (modern bread wheat), British spelt, and Romanian spelt, to drought stress were assessed in a comprehensive manner. All-around evaluations encompassed morphological characteristics, chlorophyll a and b concentrations, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, ferric reducing antioxidant power), mineral profile (iron, zinc, calcium, manganese), macronutrient profile (starch, protein, gluten, fiber), and economic yield. British spelt showed greater drought tolerance, maintaining higher chlorophyll concentration, antioxidant activity, and mineral content, especially iron, zinc, and manganese. It also showed the greatest grain protein (16.58%) and fiber (10.92%) levels during stress. WH 1080 held superior grain starch (64.30%) and gluten (27.14%) levels, maintaining industrial viability even with compromised antioxidant capacity. Romanian spelt had intermediate adaptability, with particularly consistent antioxidant activity (FRAP: 66.08 µM AA/g dry weight). Drought-induced decreases in photosynthetic pigments and morphological traits were consistent with changes in grain nutrient profiles. Correlation matrices, principal component analysis, and heatmap analyses indicated genotype-specific approaches of nutrient enrichment under stress. These findings provide meaningful insight into key trade-offs between yield properties and nutritional improvement in wheat, indicating that spelt genotypes, especially British spelt, are good sources of genetic material for breeding wheat for improvement in drought resistance and grain nutrition. This multi-trait approach is supportive of the necessity of multi-trait evaluations to provide crop sustainability under climate variation.