The risk of having extreme weather events, such as intense rainfalls or heat waves, has increased over the last decades. As the higher frequency of storms is associated with increased temperatures, the possibility of crops being exposed to waterlogging and high temperatures will increase. Wheat is crucial for food security and will be more frequently exposed to these constraints, even in Mediterranean regions, leading to substantial economic damage.

The aim of this study was to find out whether a previous event of waterlogging might reduce crop tolerance to a subsequent high temperature event or if it can confer tolerance to reduce the impact of another stress later. Thus, we conducted an experiment sowing three bread (Artur Nick, Santaella, Acorazado) and three durum (Euroduro, Don Ricardo and Athoris) spring wheats individually in plastic tubes (8.5 cm diameter and 100 cm length) outdoors.

Four treatments were imposed: control, waterlogging (for 15 days at stem elongation, DC30), heat stress (for 15 days at booting, DC40) and a treatment combining both stresses. At the end of each treatment, plants continued growing in unstressed conditions until maturity, when yield and its components (biomass and harvest index; numerical components) were quantified.

We found genotypic variability in yield responses to the stresses but not related to the different species. Yield was reduced compared to controls in all treatments by 33.7±7.3, 24.7±7.8, and 44.9±6.4% (average of 6 genotypes) when affected by waterlogging, heat stress, and both stresses combined, respectively. In general terms, a previous expose to waterlogging conferred a sort of stress acclimation to subsequently face high temperatures (resulting in an antagonistic interaction between stresses (i.e., yield reductions in the combined treatment were lower than the sum of the decreases provoked by each stress separately).

Considering the effects of individual stresses, yield seemed more sensitive in durum than in bread wheat. Treatments reduced yield mainly through decreasing grain number (mostly though the number of grains per spike) with more exceptional effects through grain weight.

Additionally, the stresses seemed to have a greater effect on overall plant growth than on yield partitioning. Understanding the impact of these stresses and their interactions is crucial not only due to genotypic variability, which aids in selecting more stress-tolerant varieties, but also because of the interactions between these successive constraints.

The antagonistic interaction observed in our experiment offers insights into mitigating the impact of concurrent waterlogging and high temperatures in wheat cultivation scenarios.