University of Isfahan Taxonomy and Biosystematics 3115-9001 14 52 2022 09 23 Introducing High-yielding Populations of Native Species of the Genus Thymus in Iran معرفی جمعیت‌‌های پرمحصول گونه‌‌های بومی سردۀ آویشن در ایران 63 76 27165 10.22108/tbj.2022.135163.1212 EN Seyed Ahmad Mousavi Ph.D. Student of Department of Plant Sciences, Faculty of Biological Sciences, Kharazmi &lrm;University, Tehran, Iran. &lrm; Farrokh Ghahremaninejad Professor, Department of Plant Sciences, Faculty of Biological Sciences, Kharazmi University, Tehran, Iran Journal Article 2022 09 20 Natural essential oils derived from plants are of significant importance in various markets, including agricultural, pharmaceutical, healthcare, cosmetics, and hygiene industries. Among aromatic plants, thyme holds a special significance. Thyme essential oil, which can be yellow, brownish, or reddish-brown, is obtained through the distillation of leaves and flowers of Thymus vulgaris and other thyme species. It has a range of applications in the healthcare and cosmetic industries. Therefore, exploring different types of thyme for essential oil production is of interest to various industries. A comparative study of dry matter and essential oil production among 108 populations of 9 Iranian thyme species and 4 populations of agricultural thyme (T. vulgaris) revealed that native Iranian thyme species possess significantly higher economic and pharmacological potential than T. vulgaris. Specifically, certain populations of T. kotschyanus and T. daenensis demonstrated higher yields of dry matter and essential oils. The selection of germplasm for cultivation and use could be strategically aligned with the intended product application. For instance, if the aim is to produce thyme as a seasoning or spice, then population 104 of T. kotschyanus, population 60 of T. fallax, population 91 of T. kotschyanus, and population 107 of T. daenensis are suitable candidates. Conversely, for essential oil extraction, population 104 of T. kotschyanus, population 60 of T. fallax, population 90 of T. daenensis, and population 67 of T. fedtschenkoi are preferable. Introduction Thyme essential oil is a dark yellow or reddish-brown liquid with a strong, pleasant smell and a sharp, persistent taste, obtained through the distillation of the leaves and flowering branches of Thymus vulgaris L. and other thyme species. Approximately 40% of its volume consists of phenols (thymol and carvacrol), along with a small amount of cymene and linalool. The genus Thymus L. exhibits significant species diversity, encompassing 220 to more than 250 species globally, distributed in the northern temperate region from Greenland to Kamchatka. The most important centers of its diversity include the Mediterranean region and West Asia. In Iran, Thymus comprises 18 species, with four (T. persicus, T. marandensis, T. daenensis, T. lancifolius) being endemic. Studying the chemical diversity of different populations, at both interspecific and intraspecific levels, remains a crucial goal in plant phytochemical research, aimed at discovering chemical types with optimal amounts of known compounds or new compounds of medicinal value. Materials and Methods Seeds from 108 populations of 9 native thyme species, along with 4 populations of cultivated thyme from various regions of Iran, were obtained. In the winter of 2009, these seeds were sown in a greenhouse, and in the subsequent spring, they were transferred to a research farm. Seedlings were planted on the farm in three replicates using a completely randomized block design and were cultivated for 3 years under identical agricultural conditions. In the fourth and fifth years, the stems were harvested and dried in the shade at room temperature. The dry weight of the samples was measured using a digital scale. Essential oil extraction was carried out using water and a Clevenger apparatus for three hours. Active ingredients were separated using gas chromatography connected to a mass spectrometer (GC-MASS). Spectra identification was conducted using inhibition indices and the injection of normal hydrocarbons (C7-C25) under identical conditions, along with the injection of essential oils, analyzed by a computer program in BASIC language. This study compared the amounts of 10 important chemicals, namely p-cymene, 1,8-cineol, δ-terpinene, linalool, thymol, carvacrol, borneol, geraniol, α-terpineol, geranylacetate, and α-terpinyl acetate. Data on the yield of dry matter and essential oil from thyme germplasms were compared over several years using SAS software version 2002 in a completely randomized block design. Results and Conclusion The data analysis revealed the average weight of dry matter and essential oil among different thyme germplasms. However, the dry matter production of each genotype over two consecutive years did not show significant differences. Among the four samples of cultivated thyme, accession 37 exhibited the highest production of essential oil and dry matter, surpassing other cultivated samples; hence, native samples were compared with this accession. All nine native thyme populations demonstrated higher average essential oil production per individual plant than the cultivated thyme under identical conditions. The highest essential oil yield was observed in T. kotschyanus. Additionally, the analysis of thymol content in the essential oil from the studied thymes indicated that T. migricus is essential oil had the highest percentage of thymol, the highest reported percentage among any thyme species. These findings suggest that the choice of germplasm for thyme cultivation can vary based on the intended use. If the goal is to produce dry matter for seasoning or similar purposes, populations such as 104 of T. kotschyanus, 60 of T. fallax, 91 of T. kotschyanus, and 107 of T. daenensis are recommended. Conversely, for higher essential oil production, populations like 104 of T. kotschyanus, 60 of T. fallax, 90 of T. daenensis, and 67 of T. fedtschenkoi are preferable. Financial Support This research did not receive any specific financial support that needs to be disclosed.

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