Changes in phenolic compounds and secondary volatile components of Kelussia odoratissima Mozaff. as affected by regeneration methods, plant growth regulators and light-emitting diodes.

Kelussia odoratissima Mozaff (celery) is a valuable endemic spice and aromatic plant of the Apiaceae family, rich in secondary metabolites. This study aimed to optimize in vitro regeneration methods and LEDs to enhance the phenolic compounds and chemical composition of Kelussia. Various combinations and concentrations of plant growth regulators (PGRs) were tested using three types of explants: cotyledons, hypocotyls, and zygotic embryos. In the second part of the study, five light treatments were tested: viz. red, blue, red‒blue, white, and control. Secondary volatile oil compounds were analyzed using solid‒phase microextraction (SPME) arrow to assess changes under each light condition. HPLC analysis identified the principal phenolic and flavonoid compounds in the different explants, such as caffeic acid, chlorogenic acid, and rutin. In particular, the highest concentration of phenolic compounds (caffeic acid: 43.09 µg/g) was detected in zygotic embryo explants treated with 2–4-D at 0.5 mg/L and BAP at 0.25 mg/L. The SPME analysis revealed that (E)-farnesene (32.09%), (Z)-ligustilide (19.4%), and pentylbenzene (14.5%) were the most abundant components. Additionally, the highest (Z)-ligustilide content was obtained in zygotic embryos exposed to red light. Finally, the in vitro culture of zygotic embryos under red LEDs offers an effective method for the in vitro production of this endangered spice plant, facilitating the production of secondary metabolites, such as phenolic compounds.