Investigating the Impact of Cultivar and Altitude on Volatile Compound Profiles and Related Gene Expression in Common Avocado Cultivars Grown in Lebanon

Abstract

Fruit aroma is shaped by a complex blend of volatile organic compounds (VOCs). In climacteric fruits like avocado, VOC production increases during ripening after harvest, ultimately influencing the fruit’s final flavor and aroma quality. Both genetic and environmental factors have been shown to influence the composition and concentration of these aroma compounds. This study investigated the effects of cultivar and altitude on the volatile profiles of seven avocado cultivars (Fuerte, Hass, Horshim, Pinkerton, LambHass, Ettinger and Reed) grown at four different altitudes in Lebanon: Abbasiyeh (158m), Ansar (302m), Nmeiriyeh (320m), and Marwaniyeh (340m). Volatile compounds were extracted and analyzed using Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry (SPME-GC-MS), and Principal Component Analysis (PCA) was used to examine variations in volatile profiles across cultivars and locations. Additionally, gene expression analysis was conducted on key genes involved in the biosynthesis of volatile compounds. PCA results revealed that the seven avocado varieties clustered into four distinct groups: Fuerte, Hass, and Horshim grouped together; Pinkerton and LambHass formed a second cluster; while Reed and Ettinger each constituted separate groups. This grouping suggests that Fuerte, Hass, and Horshim shared similar volatile profiles, as did Pinkerton and LambHass, whereas Reed and Ettinger exhibited distinct volatile compositions. These findings align with gene expression analysis, where cultivars with similar profiles also shared comparable gene expression patterns. Regarding altitude, variations in volatile profiles were less pronounced than those observed across cultivars. Notably, samples from Abbasiyeh, the lowest-altitude location, exhibited the greatest variation in volatile composition compared to other locations. At the genetic level, samples from Abbasiyeh and Ansar shower the most significant variation. These results highlight the biochemical diversity of avocado cultivars and altitude-induced variations, which could influence flavor profiles, consumer preferences, and breeding strategies.