Short-day Onion Cultivars Differ in Bulb Selenium and Sulfur Accumulation which Can Affect Bulb Pungency

The close chemical similarity of S and Se allow for antagonistic behavior between the two elements. To determine variation for Se accumulation within onions, sixteen short-day cultivars were grown under high level (2.0 mg Na2SeO4 per litre) and no Se treatments. Selenium accumulation in bulb tissues was cultivar dependent, ranging from 60 to 113 µg Se per g dry wt. High Se fertility enhanced bulb S accumulation. Pungency was reduced in some cultivars grown under Se fertility when compared to the no Se treatment indicating that although S uptake was enhanced, S metabolism in the flavour precursor biosynthetic pathway was affected. The existing variability in onion Se uptake and accumulation have important implications for Se intake in mammalian diets.