Biplot analysis of the genetic variation in the essential oil profile of Iranian landraces of Anethum graveolens

This study evaluated four landraces of local dill (Anethum graveolens) from Ardabil, Moghan, Mashhad, and Kerman, with the objective of assessing genetic and phytochemical variabilities. Plants were cultivated under field conditions on loamy soil and harvested at full flowering, the stage associated with maximum production of essential oil. Essential oils were extracted from leaves and flowers using low-temperature oven drying (40°C) and assessed via gas chromatography-mass spectrometry for measuring major constituents, including carvone, limonene, α-phellandrene, myristicin, dill ether, and dillapiole. Genotype × trait biplot analysis explained 82% of the total variation, and positive associations were observed between myristicin and dill ether, as well as between α-terpinene and α-pinene, while negative correlations were found between these compounds and α-terpinolene, dibutyl phthalate, and other minor constituents. Trait discrimination and representativeness analyses identified β-pinene and sabinene as the most informative for differentiating genotypes, followed by 1-terpineol, 5-hydroxymethylfurfural, and 5-epi-neointermedeol. Although highly abundant, such traits as essential oil, carvone, and limonene exhibited low discriminative potential. Among genotypes, Moghan displayed the highest essential oil, D-carvone, and l-limonene content, consistent with a seed-type chemotype dominated by carvone and limonene. Ardabil was rich in myristicin, dill ether, and α-phellandrene, representing a herb-type chemotype. Mashhad emerged as the most favourable genotype overall, combining desirable essential oil yield with moderate stability, while Kerman exhibited a high and stable dillapiole content, making it suitable for applications requiring consistent essential oil quality.