Modelling the nutritional implications of ozone on wheat protein and amino acids

Abstract. Ozone (O₃) pollution reduces wheat yields as well as the protein and micronutrient yield of the crop. O₃ concentrations are particularly high in India, and are set to increase, threatening wheat yields and quality in a country already facing challenges to food security. This study aims to improve the existing DO₃SE-CropN model to simulate the effects of O₃ on Indian wheat quality by incorporating antioxidant processes to simulate protein, and the concentrations of nutritionally relevant amino acids. As a result, the improved model can now capture the decrease in protein concentration that occurs in Indian wheat exposed to elevated O₃. The structure of the modelling framework is transferrable to other abiotic stressors and easily integrable into other crop models, provided they simulate leaf and stem N, demonstrating the flexibility and usefulness of the framework developed in this study. Further, the modelling results can be used to simulate the FAO recommended metric for measuring protein quality, the DIAAS, setting up a foundation for nutrition-based risk assessments of O₃ effects on crops. The resulting model was able to capture grain protein, lysine and methionine concentrations reasonably well. As a proportion of dry matter, the simulated percentages ranged from 0.26 % to 0.38 % for lysine, and from 0.13 % to 0.22 % for methionine, while the observed values were 0.16 % to 0.38 % and 0.14 % to 0.22 %, respectively. For grain and leaf protein simulations, the interdependence between parameters reduced the accuracy of their respective relative protein loss under O₃ exposure. Additionally, the decrease in lysine and methionine concentrations under O₃ exposure was underestimated by ~10 percentage points for methionine for both cultivars, and by 37 and 19 percentage points for lysine for HUW234 and HD3118 respectively. This underestimation occurs despite simulations of relative yield loss being fairly accurate (average deviation of 2.5 percentage points excluding outliers). To provide further mechanistic understanding of O₃ effects on wheat grain quality, future experiments should measure nitrogen (N) and protein concentrations in leaves and stems, along with the proportion of N associated with antioxidants, which will aid in informing future model development. Additionally, exploring how grain protein relates to amino acid concentrations under O₃ will enhance the model’s accuracy in predicting protein quality and provide more reliable estimates of the influence of O₃ on wheat quality. This study builds on the work of Cook et al. (2024) and supports the second phase of the tropospheric O₃ assessment report (TOAR) by investigating the impacts of tropospheric O₃ on Indian wheat and the potential of this to exacerbate existing malnutrition in India.