Effects of iodine and selenium biofortification on Ocimum basilicum L. nutritional quality

Biofortification of crops with beneficial micronutrients like selenium (Se) and iodine (I) is a promising strategy to enhance nutritional quality while addressing global dietary deficiencies. This study investigates the synergistic effects of foliar selenium and iodine application on basil, focusing on its nutritional composition and essential oil profile. A commercial greenhouse experiment was conducted using a factorial randomized complete block design with three replications. The experiment involved sixteen treatments including different combinations of selenium (as Na₂SeO₄) at 0, 0.5, 1.5, and 3 mg L^-1 and iodine (as KI) at 0, 0.1, 0.2, and 0.4 µM. The combined biofortification, particularly the Se₃-I_0.4 treatment (3 mg L^-1 Se + 0.4 µM I), was identified as the most effective. This optimal combination led to a 91% increase in leaf iodine content (332 vs. 174 µg kg^-1.dw^-1 in control) and increased the leaf selenium content to 17.72 µg kg⁻¹, up from 12.70 µg kg⁻¹ in the control. We observed significant increases in chlorophyll a (∼40%), chlorophyll b (∼43%), carotenoids (∼195%), and the activity of antioxidant enzymes superoxide dismutase and ascorbate peroxidase compared to the control. The treatment also altered the essential oil profile, increasing the concentration of the desirable aroma compound linalool by ∼58% while decreasing 1,8-cineole and eugenol. In conclusion, the combined foliar application, especially at the Se₃-I_0.4 level, effectively enhanced the nutritional and antioxidant quality of basil, presenting a promising strategy for micronutrient biofortification.