Document Type : Research Paper

Authors

• Maryam Kiani ¹
• Mohammad Abdoli ²
• Mehdi Ghabooli ³

¹ Department of Plant Production and Genetics, Faculty of Agriculture, Malayer University, Malayer, Iran

² Assistant Professor, Department of Plant Production and Genetics, Faculty of Agriculture, Malayer University, Malayer, Iran

³ Associate Professor, Department of Plant Production and Genetics, Faculty of Agriculture, Malayer University, Malayer, Iran

Abstract

     Background and objectives: Applying biotic and abiotic elicitors effectively enhances the biosynthesis and accumulation of valuable plant metabolites. This study aimed to assess the combined effects of yeast extract, salicylic acid, culture filtrate, and a cell homogenate derived from Serendipita indica on the essential oil content, chemical composition, and selected physiological characteristics of lemon balm (Melissa officinalis L.).
Methodology: The experiment used a completely randomized design with 15 treatments and three replications in the research greenhouse at Malayer University in 2021. The experimental treatments included foliar application of distilled water (control), salicylic acid (320 mg L⁻¹), yeast extract (1 g L⁻¹), salicylic acid (320 mg L⁻¹) combined with yeast extract (1 g L⁻¹), salicylic acid (320 mg L⁻¹) combined with culture filtrate (½ v/v), yeast extract (1 g L⁻¹) combined with culture filtrate (½ v/v), salicylic acid (320 mg L⁻¹) combined with cell homogenate (40 or 80 mg L⁻¹), yeast extract (1 g L⁻¹) combined with cell homogenate (40 or 80 mg L⁻¹), salicylic acid (320 mg L⁻¹) combined with yeast extract (1 g L⁻¹) and cell homogenate (40 or 80 mg L⁻¹), salicylic acid (320 mg L⁻¹) combined with culture filtrate (½ v/v) and cell homogenate (40 mg L⁻¹), yeast extract (1 g L⁻¹) combined with culture filtrate (½ v/v) and cell homogenate (40 mg L⁻¹), and the combination of salicylic acid (320 mg L⁻¹), yeast extract (1 g L⁻¹), culture filtrate (½ v/v), and cell homogenate (40 mg L⁻¹). The elicitors were applied as foliar sprays to the aerial parts of lemon balm plants at the 40% flowering stage. Essential oil was extracted by hydrodistillation using distilled water and analyzed by gas chromatography–mass spectrometry (GC–MS). Essential oil content and chemical composition were determined, along with physiological traits, including photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids), proline, malondialdehyde, soluble sugars, total phenolic compounds, and total flavonoids. Pearson’s correlation coefficients (r) were calculated to assess the relationships among the measured traits.
Results: A total of 38 chemical compounds were identified in the essential oil extracted from the aerial parts of lemon balm. The major constituents of the essential oils were citronellal (6.1–13.5%), trans-carveol (5.0–10.6%), citral (3.9–10.1%), linalool (4.2–9.3%), and γ-3-carene (4.2–9.2%), respectively. The combined treatment consisting of salicylic acid (320 mg L⁻¹), yeast extract (1 g L⁻¹), culture filtrate (½ v/v), and cell homogenate (40 mg L⁻¹) produced the most pronounced increases in essential oil content and the concentrations of its major constituents. Compared with the control, this treatment increased essential oil content by 63% and increased citronellal, trans-carveol, citral, and linalool by 2.20-fold, 2.12-fold, 2.59-fold, and 2.21-fold, respectively. The lowest values for these traits were recorded in the control treatment. The elicitor treatments significantly affected soluble sugar, malondialdehyde, proline, and flavonoid levels. Correlation analysis revealed significant positive correlations at the 1% probability level between essential oil content and the major essential oil constituents linalool (r = 0.971**), trans-carveol (r = 0.983**), citronellal (r = 0.988**), and citral (r = 0.984**). In contrast, essential oil content was significantly negatively correlated with γ-3-carene (r = −0.990**). Heatmap analysis of the studied traits revealed a clear separation between the control and the combined biotic and abiotic elicitor treatments.
Conclusion: The results indicated that essential oil content and the concentrations of its major constituents in lemon balm were influenced by elicitors, including salicylic acid, yeast extract, culture filtrate, and cell homogenate. Overall, the combined application of two or more elicitors effectively enhanced essential oil production and the accumulation of its major constituents, particularly linalool, trans-carveol, citronellal, and citral, in lemon balm.

Keywords

• Citral
• fungus
• medicinal plant
• Melissa officinalis
• salicylic acid
• yeast extract

Main Subjects

• Improvement and breeding