Physiological Stress Indices: A Valuable Tool to Mitigate the Impacts of High Temperatures and Drought on Durum Wheat Yield and Quality

Durum wheat (Triticum turgidum L. var. durum Desf.) is one of the world's most important and widely grown cereals, playing a fundamental role in global food security. In countries where it is traditionally cultivated, abiotic stress caused by high temperatures and limited precipitation, exacerbated by the ongoing climate crisis, is the main cause of production losses quality deterioration, and uncertainty in meeting market demand. The objective of this study was to monitor, across five experimental sites, the effect of climatic variability on phenological, morpho-physiological, and agronomic parameters, using physiological stress indices such as RWC, NDVI, and SPAD. The research was conducted during the 2023/2024 season across the southern Italian landscape of Sicily, a region representative of the durum wheat cultivation scenario in hot-arid environments, and one of the main production areas. Analysis of variance (ANOVA) revealed significant differences in most parameters, with the exceptions of the number of spikelets per spike, harvest index, and test weight. In general, a decline in yield and quality was observed across all the sites, with notable variability. High temperatures and the absence of precipitation shortened the elongation-flowering and flowering-maturation stages, influencing the accumulation of growing degree days (GDD) in the more inland sites. In most environments, plants showed reduced growth (average culm height: 41.5 cm), while yields ranged from 10.0 to 27.0 q ha(-)(1). Quality parameters, such as yellow pigment (22.9%-24.3%), protein content (13.6%-15.8%), and gluten content (8.8%-11.9%), were variable depending on environmental conditions. Finally, Pearson's correlation analysis showed strong positive correlations between physiological parameters (SPAD, RWC, NDVI) and yield (r >= 0.8), between the yellow index and yield (r > 0.8), and strong negative correlations between proteins, dry gluten, and yield (r < -0.8). Although durum wheat is drought-tolerant, it is affected by water and thermal stress, which causes spatial and temporal variability in production. Monitoring cereal systems and adopting appropriate techniques could mitigate this vulnerability, supporting cereal farming businesses.