In the recent studies two Foeniculum vulgare Mill. populations (Hungarian and Korean) had been studied in open field trials in 1997-98 in Budapest for the identification of their essential oil characteristics. The essential oil accumulation level as well as the composition of the oil were studied during ontogenesis and at 6 phases of the umbel development from budding to overripening.

In the vegetative phases, the accumulation level of the essential oil was higher in the Hungarian genotype. In the leaf rosette stage, anethole is the main compound in both genotypes (40-96%), except the root of the Korean populations which contains 54% dillapiol. The accumulation level of anethole is slightly decreasing, while dillapiol is slightly increasing during the ontogeny. a- and [3-pinenes are characteristic compounds of the leaves, especially in the Korean genotype (10-11%). Before seed setting, fenchone was present in a considerable amount (7.5%) only in the umbels of the Hungarian genotype.

During the generative development, the maximum values of essential oil content are reached at the milky fruit stage (10,11%) in the Hungarian. and at the green fruit stage (7.1% ) in the Korean type, while the composition of the essential oil changed only slightly. The ratio of fenchone is increasing after flowering and being stable during ripening. Anethole varies to a smaller extent in the umbels, only.

We proved, that the dinamics of essential oil accumulation and the oil composition may vary according to genotype. Based on our results, the Korean population is characterized in the system of Bernáth et al. (2) as a high anethol-low methyl chavicol chemoform of the anethol chemovariety (fenchone<15%; anethole>68%; methyl chavicol< 3,2%).