Common wheat (Triticum aestivum L.) stands as a cornerstone of global human nutrition, yet its vulnerability to leaf rust infections, instigated by Puccinia triticina, poses a substantial threat, potentially resulting in significant yield reductions. To safeguard yields, the development and cultivation of resistant varieties emerge as the most efficacious and environmentally sound strategy.

The atmospheric CO2 concentration has almost doubled since the pre-industrial time and it can be firmly assumed, that the CO2 concentration will continue to increase in the years to come. Despite numerous studies examining the impacts of elevated atmospheric CO2 concentrations, a comprehensive investigation into its effects on infection and resistance behaviour across a diverse range of wheat varieties remains notably absent from the literature.

In the WheatFACE project, we aim to deepen our understanding of how elevated CO2 levels affect resistance mechanisms in winter wheat. In particular, we are investigating whether elevated CO2 levels increase susceptibility due to increased biomass growth from CO2 fertilisation or, conversely, reduce fungal invasion through mechanisms such as increased stomatal closure or enhanced plant resistance.

To investigate these dynamics, we exposed two different European winter wheat populations, each comprising around 200 genotypes, to different CO2 concentrations (420 ppm vs. 800 ppm) while infecting them with two particularly aggressive leaf rust isolates. The evaluation of leaf rust infestation includes both manual assessment and digital quantification of the infested leaf area using high-throughput technology. The resulting findings provide information on the influence of elevated CO2 on the severity and extent of leaf rust infection in wheat.

In addition, in a two-year field trial, we tested twelve European winter wheat varieties with different resistance behaviour to leaf rust at different CO2 concentrations under field conditions using a FACE (Free Air Carbon Dioxide Enrichment) system under field conditions. Data to date emphasise a remarkably high repeatability (h2: 0.6 to 0.9) between the respective experiments. This provides unprecedented insights into the interaction of CO2 and leaf rust infection and lays the foundation for further genetic studies.