Beneficial effect of organic and inorganic forms of selenium on yield and nutritional characteristics of beetroot

Beetroot is an essential component of human diet and a source of biologically active compounds valuable for pharmaceutical and food industry. To increase the content of essential nutrients and develop a functional food product with enhanced antioxidants, the effect of foliar sodium selenate and selenocystine supply on yield and biochemical characteristics of two table beet cultivars (Marusia and Nezhnost) was assessed. Compared to the untreated control, foliar application of 26.4 mM sodium selenate increased root yeild by 1.20-1.25 times, monosaccharide content by 1.49-2.25 times, betalain pigments by 1.56-2.17 times and total antioxidant activity (AOA) by 1.38-1.79 times, whereas the selenocystine supply increased the same parameters by 1.44-1.85, 1.64-3.4, 1.28-1.50 and 1.31-1.33 times, respectively. Compared to pulp, root peel demostrated 2-2.6 times higher levels of betalain pigments, 1.9-2.4 times higher levels of polyphenols (TP), and 1.5-2.2 times higher antioxidant activity. Significant varietal differences in biochemical characteristic changes due to organic and inorganic Se supply were recorded. Taking into account the relatively low Se biofortification levels of roots (3-3.5 in pulp and 7-12 in peel), the results prove the importance of Se application mostly to improve beetroot yield, antioxidant content including betalain pigments, and root peel utilization as a significant souce of pharmaceuticals.