Characterisation of Floral Aroma in <scp> <i>Paeonia suffruticosa</i> </scp> ‘High Noon’: Developmental Changes and Genetic Insights

ABSTRACT Floral fragrance is a major trait of ornamental crops and an important economic feature in the floral industry. Although tree peony ( Paeonia suffruticosa ) is a culturally significant and widely cultivated ornamental plant, studies on its floral scent are relatively limited. ‘High Noon’ is characterised by a unique fragrance and high fragrance content, making it a suitable material for the breeding of fragrant tree peony. In this study, we analysed volatile organic compounds (VOCs) across five flowering stages using GC–MS, identifying 57 distinct VOCs. The types and amounts of Monoterpenoid and benzenoid/phenylpropanoid compounds gradually increased, reaching a peak at full blooming, exhibiting a trend consistent with sensory perception. Odour activity value (OAV) analysis identified linalool, geraniol, 2‐hexenal, and α‐citral as key aroma compounds at full blooming stage. Differential metabolite analysis showed upregulation of monoterpenes including linalool, (Z)‐citral, geraniol, and (E)‐citral across developmental stages. Gene expression analysis via qRT‐PCR revealed that PsDXS3 , PsDXR1 , PsMDS1 , and PsHDR1 are key genes in monoterpenoid synthesis with PsTPS5 associated with geraniol synthesis. This study explored the relationship between flowering stages and aroma formation, elucidated the contribution of specific VOCs to the aroma, and highlights candidate genes responsible for floral fragrance, providing valuable insights for the genetic engineering of tree peony floral aroma.