Seasonal fluctuation of the essential oil and 1,8-cineole compound in adapted Eucalyptus species in Fars province

Eucalyptuses trees as the fast-growing forest species are native to the Pacific. This species were introduced to Iran more than 100 years ago and cultivated in the south, having perfect environment for them. This research was aimed to investigate seasonal fluctuations of essential oil and1,8-cineol content in Eucalyptus species of Fars province. The leaves of 14 Eucalyptus species were collected from Fars province in the middle of each season for two years (2007 & 2008). Afterward, essential oils were obtained by hydrodistillation method and compounds were identified by GC and GC/MS. Results showed that in each region, some of the species had the highest essential oil yield and quality; therefore due to the high essential oil content and 1,8-cineol, they could be recommended for large-scale cultivation in the region in order to extract essential oil. Studied Eucalyptus included: E. calcicultrix (Miq.) Blakely; E. camaldulensis var. camaldulensis Dehnh.; E. cornuta; E. fruticetorum; E. intertexta R.T. Baker; E. largiflorens F. Muell.; E. lesouefii; E. longicornis F. Muell.; E. oleosa F. Muell.; E. rudis Endl.; E. salmonophloia F. Muell.; E. salubaris; E. stricklandii Maiden; E. viridis. The essential oil yield of different species at different seasons differed from 1.0 to 6.8% in 2007 and 0.3 to 5.8% in 2008. According to the results, the highest oil yield in autumn (5.2%-6.4%), the highest percentage of 1,8-cineole in winter (91.4%-94%), and the best time to harvest were recorded for  E. oleosa F. Muell at Shousni, Mamasani; therefore, E. oleosa F. Muell could be recommended for cultivation as the best species.