2.1 VOO samples
Olives were taken from trees cultivated in the geographical area of Xichang, China (latitude: 27°74′74″N, longitude: 102°23′22″E, altitude: 953m asl). Previous research had demonstrated that genotype was the main contributor to variance and the influence of crop year was weak (Ceci, Mattar, & Carelli, 2017; Yu et al., 2019), the fruits used in this research were obtained in 2018. Environmental factors, the managements of olive trees, olive fruits collection and VOO extraction were described by our previous study (Yu et al., 2019). The tree ages of ‘Coratina’, ‘Koroneiki’ were 2, 7 and 11, respectively. Green fruits were handpicked from all positions of selected trees. The climate conditions of Xichang in 2018 were described in Fig. 1.