Effect of Selenium Enrichment and Type of Application on Yield, Functional Quality and Mineral Composition of Curly Endive Grown in a Hydroponic System

Selenium (Se) is an essential element for humans’ health and the recommended amount (RDA) of Se intake per adult is 55–70 µg day-1. The main source for Se intake is represented by diet, but its concentration in vegetables is generally limited with respect to human needs. The aim of this research was to assess the effect of Se application rate and type (fertigation or foliar spray) on yield, functional properties and mineral composition of curly endive grown in a hydroponic system. Five levels of Se (0.0, 1.0, 2.0, 4.0 and 8.0 µmol L-1) were supplied via fertigation or by foliar spray in the form of selenate (Na2SeO4). The results show that a Se implementation of 4 µmol Se L-1 for plants enriched via fertigation and 8 µmol Se L-1 for plants biofortified via foliar spray successfully enhanced production performance parameters such as head weight (42.6% and 27.8%, respectively), SSC (16.7% and 14.3%, respectively), ascorbic acid (33.2% and 33.7%, respectively), total phenolic (58.9% and 54.5%, respectively) and Se concentration (22.2% and 20.3%, respectively). Furthermore, leaf Se concentration in plants enriched via fertigation ranged 0.71–17.61 mg kg-1 of dry weight (DW), whereas, in plant biofortified via foliar spray leaf Se concentration ranged 0.72–12.67 mg kg-1 DW. Plants grown with the highest dosage of Se distributed via fertigation or foliar spray showed a reduction in total-N leaf concentration by 39.4% and 28.6%, respectively, compared with the non-enriched plants. Our results indicate a consumption of 47.4 g day-1 of Se-enriched curly endive grown in soilless culture and treated with 8 µmol L-1 of selenate applied via foliar spray could be suffcient to cover the human physiological needs of this element.