Autopolyploidy effect on morphological variation and essential oil content in Thymus vulgaris L.

Garden thyme (Thymus vulgaris L.) is well known for its aromatic, anti-pathogenic and antioxidant properties and is commonly cultivated for ornamental, culinary and medicinal uses. The aim of this study was to induce ployploidy in T. vulgaris in order to obtain tetraploid plants (2n = 4x = 60) with enhanced morphological traits and increased essential oil content from diploid plants (2n = 2x = 30) using in vitro-induced polyploidization. Nodal segments were treated with four different concentrations of oryzalin (20, 40, 60 and 80 mu M) for 24 and 48 h. The ploidy levels of treated and regenerated plants were determined by flow cytometry analysis. The chemical composition of hydrodistilled essential oil was analysed by gas chromatography with quadrupole time-of-flight mass spectrometry systems. Oryzalin treatment resulted in three tetraploid plants at a concentration of 80 mu M for 24 h. Obtained tetraploid plants presented several morphological changes (increased plant weight, height, leaf length, breadth and thickness) in comparison to diploid plants. Furthermore, polyploidization demonstrated an increase in the production of secondary metabolites; tetraploids yield of essential oil increased from 0.81 % to 1.19 % and the content of several main components increased, including thymol and carvacrol by 18.01 % and 0.49 %, respectively. The obtained genotype could be implemented as a new variety for commercial production of garden thyme.