Rising atmospheric CO2 concentration may imply higher risk of Fusarium mycotoxin contamination of wheat grains.

Increasing atmospheric CO2 concentration not only has a direct impact on plants but also affects plant-pathogen interactions. Due to economic and health-related problems, special concern was given thus in the present work to the effect of elevated CO2 (750 μmol mol-1) level on the Fusarium culmorum infection and mycotoxin contamination of wheat. Despite the fact that disease severity was found to be not or little affected by elevated CO2 in most varieties, as the spread of Fusarium increased only in one variety, spike grain number and/or grain weight decreased significantly at elevated CO2 in all the varieties, indicating that Fusarium infection generally had a more dramatic impact on the grain yield at elevated CO2 than at the ambient level. Likewise, grain deoxynivalenol (DON) content was usually considerably higher at elevated CO2 than at the ambient level in the single-floret inoculation treatment, suggesting that the toxin content is not in direct relation to the level of Fusarium infection. In the whole-spike inoculation, DON production did not change, decreased or increased depending on the variety × experiment interaction. Cooler (18 °C) conditions delayed rachis penetration while 20 °C maximum temperature caused striking increases in the mycotoxin contents, resulting in extremely high DON values and also in a dramatic triggering of the grain zearalenone contamination at elevated CO2. The results indicate that future environmental conditions, such as rising CO2 levels, may increase the threat of grain mycotoxin contamination.