survey on quality and quantity of essential oil cultivated accessions of thymus fedtschenkoi ronneger in province yazd

background & aim: the genus thymus belonging to the family of lamiaceae and consist over 215 different species throughout the word. eighteen species grow naturally in iran of which four species are endemic. experimental: this reseach has been carried in medicinal plants research station in yazd province with the coordinates of longitude and latitude 55 31 49 northly, 27 15 54 east to heigh of 1209 meters above sea level in the region gerdefaramarz city of yazd shahedial. in order to in 2011 year seeds 5 accession of t. fedtschenkoi collected from west azarbayejan, semnan and zanjan provinces, were planted in jifypot. the aeril parts of plants were collected 50% flowering stage and then were dried in shadow and hydro– distilled for obtaining their essential oil. analysis and identification of chemical composition of the oil were performed by gc and gc/ms. results & discussion: the highest amount of oil yield respectively were related to accession tf3 from semnan (4.2%), and lowest was related to accession tf5 from west azarbayejan(0.8%). the highest amount of oil production respectively was related to accession tf3 (32/8kg/ha) and lowest was related to tf5 (3kg/ha). results showed that maximum compositions of essential oil  thymol, p-cymen, carvacrol, borneol, terpineol, γ-terpinene, 1,8 cineol, e-caryophyllene and linalool, respectively tf1 (70/1%), tf5 (20/2%), tf4 (18/1%), tf4 (10/4%), tf3(4/5%), tf5 (4/1%), tf4 (3/6%), tf3 (3/3%) and tf5 (3/1%) generally, with regard to oil yield, oil production and main composition of essential oil accession tf3 with 4/2% and rate of oil production 32/8kg/hectare and 66/3% thymol was selected as superior accession. recommended applications / industries: since the accession tf3 yield, oil yield and thymol is high. for planting in the same climate zones is recommended.