Phenological Traits, Seed Yield, and Essential Oil Yield of Fifty Populations of Bitter Fennel (Foeniculum vulgare)

Bitter fennel (Foeniculum vulgare var. vulgare) is a preferred subspecies in the food and pharmaceutical industries due to its high seed yield and essential oil content. However, traditional populations used by most farmers are not highly productive. To meet demand, high-yielding cultivars are needed. A five-year experiment in Pakdasht, Iran, screened 50 Iranian fennel populations for maturity habit, seed yield, essential oil content, and lifespan. Results revealed three distinctive groups based on maturity habits: early (120 days to seed harvest), medium (175 days), and late (230 days). Lifespan ranged from 3 to 5 years, with early maturities having the shortest lifespan and medium to late maturities having the longest. Populations from dry and hot/cold climates were early maturities with shorter lifespans, while populations from humid and temperate climates were medium to late maturities with longer lifespans. Over the first 3 years, essential oil yields varied among maturity groups. The highest yields were from Population Fasa (early), Meshkin Shahr, and Moqhan (medium), and population Sari (late). Populations with high essential oil yields, like Meshkin Shahr, Moqhan, and Fasa, show potential and require further investigation for potential introduction to farmers.