Could buckwheat and spelt be alternatives to wheat under future environmental conditions? Study of their physiological response to drought

Drought is one of the most harmful abiotic stresses for plants. Future drought episodes are expected to increase, negatively affecting globally cultivated crops as wheat (Triticum aestivum). Together with the crop dependency, future global food security is at risk. Thus, finding alternative crops for wheat capable of resisting drought episodes is essential to ensure food supply. Spelt (Triticum spelta) and buckwheat (Fagopyrum esculentum) are two underutilized alternative crops, whose drought resistance mechanisms remain unknown. We hypothesize that both species will have drought avoidance characteristics and will have a better drought response than wheat. We grew wheat, spelt and buckwheat in a greenhouse. Drought treatment started 28 days after sowing. When wheat and spelt reached 40 % field capacity (FC), drought was kept for 1-week, while in buckwheat the drought was kept for 4-weeks at 20 % FC. Even if partially inhibited by drought, buckwheat showed an extremely higher total biomass, as well as an extremely higher water use efficiency (WUE) than wheat and spelt. Photosynthetic parameters were extremely reduced in spelt, whereas those were less affected in wheat. The reduction in osmotic potential and the use of osmotic adjustment of spelt in combination with the increases in the antioxidant metabolism indicate the prevalence of drought tolerance mechanisms. The lack of effect on antioxidant metabolism in wheat, along with the reductions in stomatal conductance and water potential indicate the use of drought avoidance mechanisms. Buckwheat showed drought avoidance mechanisms, and its physiological parameters were almost not affected by extreme drought. Overall, spelt showed strong damages under mild drought, whereas buckwheat managed to cope with extreme drought by reducing its water requirements and increasing WUE in order to ensure its photosynthetic activity. Thus, buckwheat appears to be a potential alternative to wheat for extreme drought conditions, while spelt is not.