Alternative approaches to enhance sweet basil (Ocimum basilicum L.) essential oil: Improving composition, yield, and antifungal efficacy against Botrytis cinerea Pers. with monochromatic light and ozonated water

Essential oils (EOs) gained significant attention as they represent a rich source of antioxidant and antimicrobial compounds. Consequently, companies are increasingly exploring methods to alter key metabolites by applying controlled stress, which can influence both EO composition and yield. In this study, sweet basil plants were subjected to monochromatic LED light supplementation, i.e., polychromatic (W), narrowband green (G), blue (B) and red (R), or ozonated water (OW). The extracted EOs were characterized by their chemical composition and tested in vitro against Botrytis cinerea Pers. by incorporating them into Potato Dextrose Agar at concentrations of 400 and 800 µL L⁻¹ of EOs. Results from EOs characterization revealed that different controlled stresses altered chemical class composition or total yield. Under LED light supplementation: (i) W light increased monoterpene hydrocarbons (+62 %) and oxygenated diterpenes (4-fold) percentages; (ii) R light boosted oxygenated monoterpenes (+25 %) and hydrocarbons (+54 %); (iii) G light induced oxygenated diterpenes (more than 4-fold higher); (iv) B light reduced oxygenated monoterpenes (−17 %). All LED supplementations promoted phenylpropanoids biosynthesis, while EO yield remained unchanged. Botrytis cinerea was inhibited by EOs from W, G, B and R light added at 800 µL L⁻¹ (−24, −27, −39 and −30 %, respectively). In contrast, OW irrigation altered the concentration of only few compounds, but increased yield nine-fold compared to control. Notably, the EO extracted from OW-irrigated plants exhibited a strong inhibition of B. cinerea (−71 % at 800 µL L⁻¹). In conclusion, the overall presented findings demonstrate that controlled stress modifies basil EO composition while promoting antifungal effect.