Soil Selenium Addition for Producing Se-Rich Quinoa and Alleviating Water Deficit on the Peruvian Coast

In Peru, quinoa is cultivated in agricultural systems exposed to abiotic stresses. Selenium biofortification enriches crops and enhances their defense system against water deficit. This study aimed to determine the effect of soil Se application for enhancing Se content in quinoa grains and plant tolerance under water deficit. Selenium rates were applied at 0, 0.25, 0.5, 1.0, and 2.0 mg kg⁻¹, under irrigated and water-deficit conditions. Gas exchange, SPAD index, Se content, and proline were quantified in leaves. Dry mass was recorded in grains and shoots, whereas Se content, free amino acids, total proteins, Se and macronutrient accumulation, and Se-recovery were quantified only in grains. The water deficit diminished the transpiration rate and grain dry mass, but it increased SPAD index. The grain dry mass was increased at 0.25 and 0.5 mg kg⁻¹ Se whereas it was reduced at 1.0 and 2.0 mg kg⁻¹ Se. Selenium content in grains and leaves and Se accumulation by grains increased concerning Se rates in soil water conditions. Under water deficit, the best photosynthetic rate, instantaneous carboxylation efficiency, water use efficiency, shoot dry mass, and total proteins were at 0.5 mg kg⁻¹ Se. In grains, free amino acids and N, P, and K accumulations were maximum at 2 and 0.25 mg kg⁻¹ Se, respectively. Selenium biofortification enriched quinoa grains with selenium. The antioxidant non-enzymatic activity might be one of water deficit tolerance mechanisms promoted by Se on quinoa var INIA Salcedo and would be enhanced mainly at 0.5 mg kg⁻¹ Se.