Foeniculum vulgare Mill., a herbaceous species belonging to the Apiaceae (Umbelliferae) family, is considered as a valuable plant for its pharmaceutical, aromatic and culinary properties. In this research, callus induction and variations in the amount of callus essence in hypocotyl explants of five populations including those of Germany, Turkey, Karaj, Isfahan, and Torbatjam were studied in two hormonal treatments. Two treatments were performed: 1st, the effect of explant sources on MS medium supplemented with 1 mg/liter kinetin and 0.5 mg/liter 2, 4-D; and the 2nd, the effects of 1 mg/liter BA and 0.5 mg/liter NAA, respectively. This study aimed at elucidating the chemical composition of essential oil extracted from callus, subjected in detail by using gas chromatography-mass spectrometry (GC–MS) analysis. Callus essential oil compounds of the populations were analyzed by GC-MS and a considerable variation was observed in the quantity of the essential oil components. Essential oil profiling in callus showed that the main characteristic of the oil was a high content of the limonene, fenchone, and estragole. The results of this study showed the highest level of trans-anethole, the most important secondary metabolite in fennel callus oil in the populations of Antep under BA+NAA hormonal treatment.
