Effect of Cultivar and Cultivation Year on the Metabolite Profile of Onion Bulbs (Allium cepa L.)

This study investigated the variation of metabolite profiles of onion bulbs (Allium cepa L.) depending on genetic and environmental factors. Nine onion cultivars (Corrado, Cupido, Forum, Hytech, Picador, Redlight, Snowpack, Stardust, Sturon) with different scale color and dry matter content were grown in a two-year field trial. Using a recently established metabolite profiling approach based on liquid chromatography-coupled electrospray ionization quadrupole time-of-flight mass spectrometry, 106 polar and semipolar metabolites which belong to compound classes determining nutritional, sensory, and technological quality of onion bulbs such as saccharides, flavonoids, S-substitued cysteine conjugates, amino acids, and derived gamma-glutamyl peptides were relatively quantitated in parallel. Statistical analyses of the obtained data indicated that depending on the compound class genetic and environmental factors differently contributed to variation of metabolite levels. For saccharides and flavonoids the genetic factor was the major source of variation, whereas for cysteine sulfoxides, amino acids, and peptides both genetic and environmental factors had a significant impact on corresponding metabolite levels.