variability of essential oil content and composition of different iranian fennel (foeniculum vulgare mill.) accessions in relation to some morphological and climatic factors

fennel (foeniculum vulgare mill.) is an industrial medicinal plant with different pharmaceutical and food applications. in this study, the leaf essential oil composition of 12 iranian accessions of fennel collected from different geographical regions was assessed. the essential oil yield of fennel leaves ranged from 0.65% (varamin accession) to 2.03% (tabriz accession). trans-anethole, fenchone and limonene were highly abundant in all of the examined oils. trans-anethole ranged from 41.19% in shiravan to 56.6% in shiraz accessions and had negative correlation with most of the constituents. according to the major compounds, two chemotypes were defined in which group 1 was considered as the high trans-anethole (> 50%) and group 2 was a high limonene group. the correlation of essential oil yield and trans-anethol with climatic conditions and some morphological characters were also assessed. higher temperatures and essential oil yield had negative pearson correlation (r= -0.371), while trans-anethol and high temperature showed positive correlation (r= 0.459) in fennel. furthermore, the studied accessions had different flowering time and height. the early flowering and dwarf accessions had higher essential oil yield, while the late flowering ones had higher trans-anethol in their leaves.