Light intensity management as a strategy to enhance folate accumulation in soilless baby leaf production

Folate deficiency remains a relevant public health concern, and agronomic biofortification may represent a sustainable strategy to enhance dietary intake through fresh vegetables. This study evaluated the effect of different light intensity regimes on folate accumulation, yield, mineral composition, and nitrate content in mizuna (Brassica rapa L. var. japonica), pakchoi (Brassica rapa L. subsp. chinensis), and chicory (Cichorium intybus L.) grown in a soilless system under LED lighting. Three treatments were applied over a 30day growth cycle: a constant light intensity of 200 µmol m⁻² s⁻¹ (T1); an initial 23day period at 200 µmol m⁻² s⁻¹ followed by a 7day increase to 300 µmol m⁻² s⁻¹ (T2); and a constant light intensity of 300 µmol m⁻² s⁻¹ (T3). Folate content significantly increased under T3 (+24% vs. T1 and T2), particularly in pakchoi, without affecting fresh yield. Higher light intensity also reduced NO3- accumulation (up to −80% in pakchoi), whereas no substantial changes were observed in mineral composition. A 100 g portion of mizuna (T2) or pakchoi (T3) can provide up to 45% of the adult Recommended Daily Allowance (RDA) for folate. Targeted PPFD management therefore represents a promising chemical-free strategy to enhance micronutrient density, although species and genotype selection remain crucial for effective biofortification.