Genetic Variation of Shoot Yield, Essential oil and Yield Components in Four Thyme Species

Thymus daenensis Celak, Thymus kotschyanus Boiss. & Hohen., Thymus transcaspicus Klokov and Thymus vulgaris L. are aromatic and medicinal species which due to hybridization within species and between species has high morphological diversity. A study was carried out in order to evaluate yield and yield components in 10 ecotypes of Thymus species collected from Isfahan, Markazi, Qazvin and West Azerbaijan provinces. This experiment was performed in a randomized complete block design with three replications at Research Center for Agriculture and Natural Resources Research and Education of Razavi Khorasan province. Plant height, shoot yield, 1000-seed weight, essential oils (EO) content, EO yield, number of nodes per stem, internode length and days to flowering stage were measured in all ecotypes. T. vulgaris was considered as the control. The results of analysis of variance showed that there were significant differences (p≤0.05) for days to 50 % flowering, number of nodes, internode length, plant height, stem weight, seed weight, EO content and yield among species and ecotypes within Thymus species. The highest EO content and yield among species were observed by 2.45% and 1.28 g/plant in T. vulgaris, and 2.03% and 0.84 g/plant in T.daenensis, respectively. The highest EO content was observed among ecotypes at 1.84% in T.kotschyanus, ecotype K54 and 2.32% in T.daenensis, ecotype D49. The strong and significant (P ≤ 0.01) positive correlation of EO yield was observed with EO content (r=0.88**), seed weight per plant (r=0.78**), plant height (r=0.70*), shoot yield (r=0.80**) and internode length (r=0.89**). In the principal component analysis in thyme species and ecotypes, the eigenvalues obtained from the first three main components, explain 53%, 15%, 11%, and a total of 80% of the total variance of the variables. It was concluded that the ecotypes of D49 and D72, in T.daenensis having higher EO yield were recommended for breeding improved varieties.