Folate biofortification strategy by elicitation in kale baby leaves

Humans cannot synthesize folates, so they must be acquired through dietary sources, with plants serving as a primary source. To enhance folate levels in vegetables, this study investigated the pre-harvest application of elicitors on kale ('Cavolo Nero') baby leaves under greenhouse-autumn conditions in Southern Italy.

Phenylalanine (0.37 µM) and salicylic acid (250 µM) were applied three times and compared to a water control. Folate content, alongside biometric traits (yield, leaf area and number, dry matter), bio-physiological parameters (chlorophyll content; measurements of gas exchange and chlorophyll a fluorescence), and compositional properties (nitrate, vitamin C, phenols, flavonoids, carotenoids, antioxidant capacity) were determined.

The treatments maintained yield (1.0 kg m^-2, on average), while both elicitors increased the folate concentration (1,283 µg 100 g^-1 d.w., on average) compared to the control (1,203 µg 100 g^-1 d.w.). Salicylic acid application enhanced antioxidant compounds (vitamin C, carotenoids) without modifying antioxidant capacity and nitrate levels. In contrast, phenylalanine decreased antioxidant compounds (phenols, vitamin C) along with antioxidant capacity, and enhanced nitrate level (+56%).

Considering the limited literature available on this topic, the present work provides an important first step toward producing folate-biofortified baby leaf vegetables with enhanced beneficial traits.