Boron Biofortification of Portulaca oleracea L. through Soilless Cultivation for a New Tailored Crop

Purslane (Portulaca oleraceaL.) is a wild edible plant, traditionally consumed in the Mediterranean area and recently proposed as a new ready-to-eat vegetable; it is also called the "vegetable for long life" because of the high contents of several healthy compounds. Although boron (B) is not considered to be essential for humans, a daily intake of about 2 mg to obtain positive effects on aging in adult men and women has been suggested. In this study, two genotypes of purslane (wild collected and commercial variety) are grown by using a hydroponic system with three boron (B) levels in the nutrient solution (NS) (0.3 mg/L-control, 3 mg/L-low level of biofortification, and 6 mg/L-high level of biofortification) in order to increase the B content in the edible parts of the plant. The crop yield, color traits, and content of glucose, fructose, total phenols, chlorophylls, carotenoids, mineral elements (Al, B, Ca, Cr, Fe, K, Mg, Mn, Na, and Zn), nitrate, and oxalate are analyzed. Independent of the genotype, the B content in edible purslane was successfully increased in comparison with the control, obtaining 1.8- to 10.7-fold higher values of B tissue concentrations by using, respectively, 3 and 6 mg/L of B in the NS without affecting crop performances. From a nutritional point of view, the average daily intake of B could be satisfied by consuming about 75 or 48 g of purslane, grown by using 3 and 6 mg/L B level in the NS, respectively. Apart from B and Fe, the content of mineral elements in edible parts of purslane was not strongly influenced by different B levels in the NS but it was affected by genotypes. A lower sugar content was found in wild purslane grown with the highest B level. A higher content of both chlorophylls and carotenoids was found in the control but only for the commercial genotype. No differences in oxalate content were observed among B levels in the NS, while only in the case of wild genotype, we found a lower nitrate content when a B concentration of 3 mg/L was used in the NS. In conclusion, we demonstrated the possibility of using the floating hydroponic system, combined with specific B concentrations in the NS composition, as a method to calibrate the B uptake in edible parts of purslane.