Qualitative and quantitative changes in essential oil of fennel (Foeniculum vulgare Mill.) under salinity stress

In order to study the effect of irrigation water salinity on the quantity and quality of fennel (Foeniculum vulgare Mill.) oil, and seed production, a field experiment was conducted in a split-plot based on randomized complete block design with three replications. The experimental treatments included fennel genotype at four levels (German P11-820065, European 11486, and two indigenous genotypes including Lorestan and Hamedan) and water salinity at three levels (2 (control), 5, and 8 dS/m). The results showed that the effect of salinity was significant on all traits except α-pinene, myrcene, and essential oil percentage. Genotypes showed no significant difference in anethole, α-phellandrene, γ-terpinene, percentage, and essential oil yield. The interaction of salinity× genotype had a significant effect on all traits. Genotype P11-820065 had the highest essential oil percentage (3.90%) and yield (91.41 kg ha-1), and seed dry yield (2359.7 kg ha-1) between genotypes at control salinity level. With increasing salinity level, the seed and essential oil yield in non-indigenous genotypes decreased by a slope more than that of indigenous genotypes. Moreover, the content of anethole as the most important essential oil component of fennel increased to 5 dS/m salinity and then decreased. Based on the results of this study, under irrigation water salinity conditions, indigenous genotypes had higher economic efficiency due to their higher resistance to salinity stress. Water salinity affected only the content of essential oil components, but had no effect on its composition.