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 mu g 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.