Response of Durum Wheat Cultivars to Climate Change in a Mediterranean Environment: Trends of Weather and Crop Variables at the Turn of 21st Century

A better comprehension and analysis of climate impacts on crop traits allows the implementation of more appropriate adaptation strategies and, therefore, a higher resilience of the future cropping systems. The aims of this study were: (i) to assess how the climate changed in the last 32 years in a Mediterranean-type climate, (ii) to understand how crop traits evolved over time in early and late durum wheat cultivars and (iii) to highlight which weather variables mostly affected the performances of diverse durum wheat varieties. To investigate this, a 32-year period (i.e., 1989–2020) was analysed, detecting possible significant trends of weather variables (e.g., air temperatures, precipitations, solar radiation) and crop traits (e.g., earliness, yield, yield components and test weight) over time in Viterbo, central Italy. Eight durum wheat varieties (4 early and 4 late cultivars) were chosen from the most used in that location. A clear upward trend of the monthly maximum air temperature during the entire growing season was revealed (0.12°C–0.21°C per year), while rainfall displayed a significant trend only for February and March. Days to heading and number of spikes per unit area showed a significant downward trend moving towards 2020. Anticipation of heading date was much more pronounced in the late cultivars than in the early ones, so that the difference between the two groups was reduced from about 10 days of 1989 to less than 6 days of 2020. Grain yield stagnated around 5 t ha⁻¹ with late varieties that proved to be as good producers as the early ones. Test weight and thousand kernel weight showed a slight increase over time. Maximum temperatures of February and March exerted a considerable influence in reducing time to heading (0.7–3.4 days for each additional°C), while the maximum temperature of May was detrimental for grain yield (−180 to −270 kg ha⁻¹ for each additional °C). Our study identified two weak points in the current durum wheat cultivation: (i) phenology is being more and more similar among modern cultivars; (ii) the number of spikes per unit area dramatically decreased in the last 30 years. Therefore, beside greater genetic diversity, a new agronomic approach, especially from seeding to the end of the tillering stage, will be required to cope with durum cultivation in the future climate scenario of the Mediterranean. The outputs of our analysis add precious information on the comprehension of climate change effects on Mediterranean cropping systems and can guide either the decision making for the management of durum wheat or its breeding activity for the future.