Genetic relationships between some Tunisian Citrus species based on their leaf volatile oil constituents

Volatile oil constituents of Tunisian sweet orange (Citrus sinensis Osbeck) cv. Meski (MES), Valencia Late (VAL), Thomson Navel (THN) and Maltaise Blanc (MAB); mandarin (Citrus reticulata Blanco); sour orange (Citrus aurantium L. cv. Amara (AM)) and pummelo (Citrus grandis Osbeck) were obtained by hydrodistillation and analysed by gas chromatography (GC) combined with a flame ionisation detector (FID) and mass spectrometry (MS). A total of 41 components accounting for more than 95% of the total essential oils were identified, and oxygenated monoterpenes (69.5-99.9%) were found as the most prominent fraction in all oil samples. The main constituents were linalool (3.1-73%), isoborneol (0-55.8%) and tepinen-4-ol (1.1-19.2%). A high degree of inter-and intraspecific chemical variability between species and cultivars was found to be genetically determined, and a set of distinctive traits (chemical markers) in the essential oils profile was established. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) of all identified components grouped the oils into two main chemotypes (linalool/isoborneol and isoborneol/linalool).