Survey on quality and quantity of essential oil different accessions of Thymus pubescens in province Yazd

The genus Thymus belongs to family lamiaceae and consists of 215 different species throughout the word. Eighteen species of this genus grow naturally in Iran of which four are endemic. Thymus spp. essential oil contains valuable compounds such as thymol and carvacrol, which making it very important. After cultivation of different accessions of Thymus pubescens at the station of medicinal plants research, Shahedieh Yazd, the aerial parts of the plants were collected at 50% flowering stage and then were dried in shadow using hydro – distillation to obtain their essential oil. After the determination of essential oil efficiency based on the plant dry weight, analysis and identification of chemical compounds of the oil were performed by GC and GC/MS. Results showed that the highest oil yield was related to accessions MKOMKO 3.24%), CFT (3.24%), MKOCFT (2.87 %) and the lowest was related to accession BHUZSE 0.66%). The highest oil production per hectare was related to accessions CFT (24.69 kg/ha), MKOCFT (20.8kg/ha), CFTCFT (20.17kg/ha) and the lowest was related to CFTMKO (0.9 kg/ha). The maximum content of paracymen,1,8 cineol, gamma-terpinene, borneol, thymol, carvacrol, limonene, linalool and E-caryophyllene was respectively found in accessions MKOMKO (10.73%), CFT (31.66%), MKOMKO (20.44%), MKOMKO (29.35%), CFT (60.39%), VGYVGY (47.17%), QVGY (14.1%), CFTMKO (72.3%) and VGYMKO (20.4%). Considering the oil yield, oil production and main composition of essential oil, accessions CFT with 3.24% oil yield, 24.6 kg/hectare oil production and 60.39% thymol, accession MKOMKO with 3.24 oil yield, 19.52 kg/hectare oil production and 40.26% carvacrol, and accession MKOCFT with 2.87% oil yield, 20.8 kg/hectare oil production, 33.25% terpineol and 33.11% linalool were selected as superior accessions.