Effect of Selenium Fortification on Growth Performance and Nutritional Compounds of Kale (Brassica oleracea L. Var. acephala DC.)

This study aims to investigate the effects of selenium (Se) fortification on growth performance and the Se content in kale using Se fertilizer, and it determines the influences of Se fortification on the metabolic profile of kale using quasi-targeted metabolomics. The results showed that Se fortification increased the plant height and leaf weight of kale, up-regulated the total Se content and decreased the chlorophyll and total phenolic contents in kale leaf. Se fortification elevated selenate (Se(IV)), selenite (Se(VI)), selenocystine (SeCys₂), Se-methylselenocysteine (Se-MeSeCys) and selenomethionine (SeMet) contents, as well as total contents of Se in different forms in kale leaf. Se fortification also changed the metabolic profile of kale leaf, via six particular types of compounds (amino acid and its derivatives; organic acid and its derivatives; carbohydrates and its derivatives; lipids; flavonoids; organoheterocyclic compounds) and eight metabolic pathways (alanine, aspartate and glutamate metabolism; amino sugar and nucleotide sugar metabolism; sulfur metabolism; starch and sucrose metabolism; taurine and hypotaurine metabolism; glycolysis/gluconeogenesis; fructose and mannose metabolism; nitrogen metabolism). Moreover, 24 metabolic biomarkers were screened for kale leaf affected by Se fortification. Furthermore, correlations were observed between metabolic biomarkers and Se contents as well as speciation. These results indicate that Se fortification has a significant influence on the growth performance and nutritional compounds of kale, providing references for the future study on the production and bioactivity of Se-enriched kale.