Volatomics-Assisted Characterization of Flavor Contributors During Ripening of Wallace Melon (Cucumis melo L.)

Wallace melon has a powerful, pleasant aroma when ripe. However, little is understood about the aroma profile and the Volatile Organic Compounds (VOCs) biosynthesis during ripening. The aim of this study is to investigate the metabolome and transcriptome of Wallace melon to study the mechanism underlying its aroma formation systematically. HS-SPME/GC-MS and RNA-Seq were used to analyze the VOCs and associated genes of Wallace melon from three developmental stages (i.e., green, transition, and yellow stages). The aroma profiles included 47 VOCs, which were in connection with 35 genes. Yellow- stage fruits are more aromatic than the melons in the transition and green stages, producing higher concentrations of total VOCs (2994.36 ng/g), with ethyl acetate (543.16 ng/g) being the most abundant compound. Transcriptomic analysis revealed that the biosynthesis of VOCs was mainly related to fatty acid and amino acid metabolisms. Moreover, the lipoxygenase-1 (MELO3C014482.2), alcohol dehydrogenase-2 (MELO3C017100.2), 3-ketoacyl-CoA synthase-3 (MELO3C010941.2), and hydroperoxide dehydratase (MELO3C018412.2) genes were closely related to alcohols/esters through correlation analysis. The information generated will deepen the understanding of Wallace melon storage quality and guide melon product development.