Biofortification of Ora-pro-nobis (Pereskia aculeata Mill.) Through Soil Selenium Application

Abstract

The ora-pro-nobis (Pereskia aculeata) is a nutritious native American vegetable that stands out for its high protein content. This study aimed to assess the potential of P. aculeata for selenium (Se) biofortification and accumulation by evaluating agronomic parameters, nutrients, and nutritional composition under different forms and application rates of Se via soil. The experiment was carried out in a greenhouse using two Se sources (selenate and selenite) and five application rates (0.5, 1.0, 2.0, 4.0, and 8.0 mg Se kg−1 of soil) and the control as an additional treatment. The evaluations carried out were total Se content, recovery, and uptake in stems and leaves, agronomic parameters, centesimal composition, relative chlorophyll index (SPAD), total proteins, total free amino acids, and nutrient content in leaves. Se was more strongly absorbed and accumulated in leaves and stems with selenate treatment and was significantly higher in leaves. Furthermore, phytotoxic effects were observed in plant leaves and internodes at higher application rates of selenate (4.0 and 8.0 mg Se kg−1). Selenite provided higher leaf fresh matter (LFM) and stem dry matter (SDM) than selenate at a rate of 8.0 mg kg−1. For the relative chlorophyll index (SPAD) and the percentage of ash, the rates of 4.0 and 8.0 mg kg−1 showed higher averages for selenate treatment. Lipid percentage and total free amino acid (TFA) content were higher at rates of 0.5, 1.0, and 2.0 mg kg−1 for selenate and selenite treatment, respectively. The percentage of total carbohydrates (TC) was higher under selenite application at 1.0 mg kg−1, and for selenate rates, TC was higher at 0.5 and 8.0 mg kg−1. For the total protein (TP) content, selenite was higher than selenate at application rates of 1.0 and 2.0 mg kg−1. An increase in leaf S content was observed with increasing Se application rates up to 4.0 mg kg−1 with selenate treatment. Se was significantly absorbed and accumulated in selenate-treated leaves, affecting leaf agronomic parameters, SPAD index, lipids, ashes, carbohydrates, total proteins, total free amino acids, and S content. Although non-tolerant, P. aculeata is a Se-accumulating plant. Selenate application resulted in leaf Se accumulation, reaching high Se levels at the highest rate applied (maximum ~ 970 μg g−1). Although selenate induced symptoms of phytotoxicity at the higher rates (4.0 and 8.0 mg Se kg−1), Pereskia aculeata resulted a species with potential for biofortification that can be used to supply Se to human food.