Metabolomic and transcriptomic integration reveals the mechanism of aroma formation as strawberries naturally turn colors while ripening

Aroma is an important indicator of fruit flavor, but mechanisms of aroma formation in strawberries (Fragaria spp.) during natural ripening are still not clear. In this study, aroma compounds in strawberry cultivars were analyzed using gas chromatography-mass spectrometry (GC-MS). Richly creamy strawberry cultivars in particular expressed high levels of vanillin acetate and coumarin (up-regulated by 12.6- and 9.8-fold, respectively), while the aroma-free cultivars were dominated by differential changes in terpenes and alcohols. Further research using liquid chromatography-mass spectrometry (LC-MS) and RNA-Seq indicated that the activation of the phenylpropanoid biosynthesis and alpha-linolenic acid metabolic pathways constituted the key to formation of aroma compounds in creamy strawberry cultivars. The results of this study not only provide a well-defined database to detect aroma compounds in different strawberry cultivars but also explore the underlying mechanisms of creamy aroma formation in strawberries.