Morphological traits, yield, antioxidant activity and essential oil composition of oregano as affected by biostimulant foliar applications

Biostimulants are interesting products which can promote the plant growth and improve its qualitative traits. In this research, the effects of foliar applications of four biostimulants on oregano (Origanum vulgare L.) crop have been investigated by evaluating morphological parameters, fresh and dry yield, antioxidant activity, total phenolic content, and chemical composition of essential oil. The highest plant height (78 cm), inflorescence height (22.2 cm), inflorescences+leaves dry yield (0.5 t ha-1), dry matter yield (38.3 %) and essential oil yield (3.4 %) were obtained in plants treated with biostimulant BlueN®, composted of Methylobacterium symbioticum SB23. Plants treated with Acadian MPE®, containing vitamins, amino acids and proteins, and betaines, showed the highest total phenolic content (60.3 GAE mg mL-1). The combination of 21 traits with principal component analysis (PCA) allowed to discriminate the biostimulant Biostimol Plus plus Peptamin-V Plus®, based on Ascophyllum nodosum extract and other elements as nitrogen, carbon, manganese, zinc and iron chelates, in a correlated way with p-cymene, α-thujene, α-terpinene, β-myrcene contents, showing values significantly higher. The heat-map identified two main clusters where the treatments with biostimulants were clearly separated from the control. Biostimulant treatments influenced the chemical composition of essential oil by increasing the number of components, monoterpene hydrocarbons and sesquiterpene hydrocarbons contents. Therefore, biostimulants can play an important role with a view to sustainable oregano cultivation by representing a safe source of nitrogen and especially for organic farming.