## 3 Results and Discussion
### Influence on VOOs Quality and Composition
#### 3.2.4 Volatile Compounds  
In Table 6, the volatile profile of VOOs obtained from Coratina cv. olive fruits harvested from rainfed olive trees and irrigated trees at different watering regimes is shown.  
During both years of investigation, irrigation was associated with a significant decrease in total volatile compounds, especially in particular groups of volatiles such as total C6 volatiles, as well as total aldehydes and alcohols, which are mostly involved in the specific green odor of VOOs. Regarding the concentration of the most abundant volatile compound, _E_-2-hexenal (related to the green sensory notes), it followed the trend of total volatile compounds. Moreover, in 2019 the decrease of _E_-2-hexanal and total volatile compounds was most pronounced in T\({}_{2}\) and T\({}_{3}\) treatments, while in 2020 differences among irrigated treatments were not found. Total ketones were not affected by irrigation in 2019, while in 2020 a decrease was detected in the T\({}_{2}\) and T\({}_{3}\) treatments. Total esters increased in all irrigated treatments in 2019, while in 2020 differences among treatments were not found.  
[PERSON] et al. [54] also reported that total volatiles tend to decrease with the amount of water applied (rainfed, deficit irrigation 30% EtC, and full irrigation treatments) in the study of irrigation of Cobrancosa cv. trees in Portugal. However, that effect was more pronounced in a year with severe drought than in a year with a rainy spring, thus suggesting that the tree water status influenced the volatile composition of oils not only in the oil accumulation phase but also throughout the whole crop season.  
In contrast, [PERSON] et al. [49] did not find differences in most of the investigated volatile compounds concentration between oil from rainfed and waste water irrigated treatments (20 and 40% EtC) of Chemlali olive trees grown in Tunisia, except for a slight decrease in octanal and acetic acid concentration in irrigated treatments.  
Even though there have been reports that soil water availability could have an influence on the VOO volatile composition [16; 55], it seems that the effect of irrigation is cultivar dependent [17]. [PERSON] et al. [17] found that total volatiles increased as the amount of supplied water decreased in Arbequina oils, while they increased in Coratina oils and for Koroneiki oils the highest volatile content was observed with a restitution of 75% Et\({}_{\text{c}}\). Therefore, [PERSON] et al. [17] concluded that there was no general trend in total volatile changes due to the irrigation regime applied.  
From Table 6 it is evident that growing season influenced the concentration of volatile compounds, with generally higher concentration of volatiles in 2020. Although, according to the meteorological station, 2020 had less precipitation overall compared to 2019 [23], higher precipitation in the ripening period in 2020 (Figure 1) could have led to the higher concentration of volatiles determined in that year. [PERSON] et al. [16] concluded also during their three year investigation of Frantoio cv. tree irrigation that the changes of volatile compounds concentration in olive oils were more dependent on growing season conditions than irrigation regimes. Despite that, [PERSON] et al. [16] found that some volatiles could be related to the water status of olive trees; _E_-2-hexen-1-al was higher in fully irrigated trees than in watering stressed trees, and higher concentration of aldehydes were found in the irrigated Frantoio cv. trees (full and deficit irrigation), which does not align with our results on volatiles in irrigated Coratina cv. oils.