Effects of the foliar application of selenite at different growth stages on selenium transformation, silage quality and the metabolome of tiger nut (Cyperus esculentus L.).

Tiger nut (Cyperus esculentus L.) is a valuable source of nutrient-rich leaves and bulbs, and the production of selenium-enriched tiger nuts may effectively supplement selenium for both human and animal nutrition. Here, we biofortified tiger nuts via the foliar application of sodium selenite at three growth stages and investigated the resulting nutritional quality and metabolic pathways to determine the optimal treatment period. The findings indicate that selenium application markedly increased total selenium levels, particularly during the grain formation stage, with increases of 1248.03% and 1251.82%, respectively. It enhanced fermentation quality by increasing the crude fat, lactic acid and acetic acid contents and reducing the crude fiber content. Metabolomic analysis revealed significant increases in amino acid, derivative, and flavonoid contents in the bulbs at this stage. Consequently, the foliar application of selenium at the grain formation stage is optimal to produce selenium-enriched tiger nuts.