Genetic Variation in Essential Oil Constituents of Fennel (Foeniculum vulgare Mill) Germplasm

Ninety one fennel (Foeniculum vulgare Mill.) germplasm lines collected from various geographical locations in India were evaluated for their essential oil content and its composition. Essential oil content ranged from 1.0 to 3.3 %. Maximum lines had 2-3 % essential oil. In all the germplasm lines eleven major compounds including alpha-pinene, camphene, beta-pinene, myrcene, cymene, gamma-terpinene, 4-allyl anisole/ methyl chavicol or estragol, anethole, geranyl acetate and p-anisaldehyde were detected. Anethole was most abundant compound in all fennel germplasm lines which ranged from a minimum of 9.15 % to a maximum of 96.64 % with an average of 44.33 %. Another predominant compound observed in essential oil of fennel germplasm lines was 4-allyl anisole/methyl chavicol or estragol, content of which ranged between 2.04 to 83.01 %. A group of terpenoids consisting of alpha-pinene, camphene, beta-pinene, myrcene, cymene and gamma-terpinene accounted for 0.18 to 18.66 % of essential oil of which gamma-terpinene was contributed from a minimum of 0.13 % to a maximum of 14.95 %. A significant negative correlation (r = -0.98) was observed between related compounds anethole with 4-ally anisole and gamma-terpinene (r = -0.42). Further, the germplasm lines were grouped in different classes as per major essential oil constituents viz., anethol, gamma-terpinene and 4-allyl anisole. Cluster analysis was done using ward's method based on the value of gamma-terpinene, 4-ally anisole and anethole+estragol which resulted in to seven distinct groups of 91 germplasm lines.