Varietal screening of ozone sensitivity in Mediterranean durum wheat (Triticum durum, Desf.)

This study investigated the ozone (O3) sensitivity of five cultivars of durum wheat (Triticum durum) grown in Open-Top Chambers (OTC) during the 2013 growing season. Two levels of ozone were applied during daylight hours:+50% and-50% of ambient ozone concentration respectively in O3-enriched OTC and charcoal-filtered OTC. Results suggest that the significant differences observed in agronomic parameters, were more cultivar-dependent rather than ozone-dependent. Two cultivars showed a significant reduction of aboveground biomass due to ozone (-19.7% and-25%), however only one of them showed also a significant reduction in grain yield (-16%). Stomatal conductance was significantly reduced by ozone fumigation up to-33% in the afternoon measuring cycle. No significant effects on chlorophyll fluorescence were found, nor correlation was observed between ozone-like symptoms severity (leaf chlorotic/necrotic spots) and yield reduction, suggesting that these parameters cannot be indicative of ozone sensitivity/tolerance. These results may be useful for the selection of durum wheat genotypes more adapted for the cultivation in geographical areas where tropospheric ozone is particularly high, but also for the future definition of consistent dose-response relationships to be used in the ozone risk assessment evaluation for the Mediterranean countries