Phytotoxic Ozone Dose-Response Relationships for Durum Wheat ( Triticum durum , Desf.).

Ozone (O 3 ) pollution poses a significant threat to global crop productivity, particularly for wheat, one of the most important staple foods. While bread wheat ( Triticum aestivum ) is unequivocally considered highly sensitive to O 3 , durum wheat ( Triticum durum ) was often found to be more tolerant. This study investigated the O 3 dose-response relationships for durum wheat in the Mediterranean region, focusing mainly on grain yield losses, and utilizing the phytotoxic ozone dose (POD) metric to describe the intensity of the stressor. The results from two experiments with Open-Top Chambers performed in 2013 and 2014 on two relatively sensitive durum wheat cultivars confirmed that this wheat species is far more tolerant than bread wheat. The use of a local parameterization of a stomatal conductance model based on field measurements did not significantly improve the dose-response relationships obtained in comparison to the generic parameterization suggested by the Mapping Manual of the United Nations Economic Commission for Europe (UNECE). The POD6 critical level of 5 mmolO 3 m -2 for 5% grain yield loss was remarkably higher than the one established for bread wheat with analogous experiments, highlighting that O 3 risk assessments based on bread wheat may largely overestimate the damage in the Mediterranean region where durum wheat cultivation prevails.