Effect of sowing time and soil water content on grain yield and phenolic profile of four buckwheat (Fagopyrum esculentum Moench.) varieties in a Mediterranean environment

Four varieties of buckwheat (Fagopyrum esculentum Moench), Aizu, Botan, Hitaci and Kitawase, were evaluated using two sowing times and two irrigation treatments in a Mediterranean environment in order to ascertain a possible adaptation of this crop to this environment. Buckwheat is cultivated in particular for the high protein content and for its good biological value compared to common cereals, and for its high levels of phenolic compounds. In addition, it is gluten-free and thus suitable for people suffering from celiac disease. Overall the 4 buckwheat varieties tested in this study showed high protein content (14%, on average), although grain yield was low (420 kg ha−1, on average). Yield was affected by sowing time and irrigation treatment, whereas protein content was related to the variety. Low irrigation treatment (“water stress”) resulted in a lower yield (325.9 kg ha−1) and lower protein content (13.7%) compared to full irrigation treatment (514.7 kg ha−1 and 14.3%, respectively), but also in a higher content of phenolic compounds (4.46 vs. 2.79 mg/g). Grain yield and phenolic fingerprint of buckwheat seeds were investigated in order to establish differences and similarities related to variety, sowing time and soil water content.