Floral Volatile Organic Compounds of Chinese Cymbidium Orchids: From Biosynthesis and Function to Genetic Regulation

Chinese Cymbidium orchids (Cymbidium spp.), collectively known as Guolan, are highly valued ornamental plants renowned for their elegant and persistent floral fragrance. Floral scent contributes to pollinator attraction, plant defense, and ornamental and commercial value. This review summarizes the composition of floral volatile organic compounds (VOCs), scent-emitting tissues, and spatiotemporal emission patterns in major cultivated Chinese Cymbidium orchids, including C. goeringii, C. faberi, C. ensifolium, C. sinense, and C. kanran. Floral scent emission exhibits strong tissue specificity and is dynamically regulated by floral developmental stages and circadian rhythms. Emphasis is placed on the biosynthesis and genetic regulation of the two dominant volatile classes, terpenoids and fatty acid derivatives. Current evidence indicates that terpenoids, especially sesquiterpenes, and fatty acid derivatives, particularly methyl jasmonate, are the major fragrance components, although their composition and abundance vary considerably among species. At the molecular level, terpene synthases and jasmonic acid carboxyl methyltransferase play central roles in characteristic scent formation, while multiple transcription factors regulate their expression. Future studies should clarify phenylpropanoid and benzenoid volatile biosynthesis, develop stable genetic transformation systems, and integrate multi-omics and ecological approaches to support fragrance-oriented breeding and germplasm utilization.