Identification and molecular mechanism analysis of volatile compounds in three kinds of aromatic Brassica Chinensis

The aromatic quality of non-heading Chinese cabbage ( Brassica chinensis L., NHCC) vars Xiangqingcai (XQC), is significantly enhanced when cultivated in China's Suzhou region. To investigate the chemical and molecular basis of this characteristic fragrance, an integrated analysis of volatile organic compounds (VOCs), and transcriptomes from three key Xiangqingcai (XQC) cultivars (black leaf [FB], yellow leaf [FH], and Xiuhuajin [FX]) were performed using headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME-GC-MS) and RNA sequencing, with Suzhouqing (SZQ) as the control. Comparative analysis identified 56 VOCs with significantly different abundances between the XQC cultivars, and SZQ. Thirteen of these were identified as key aroma-active compounds, belonging to diverse chemical classes including nitriles, terpenes, alkenes, aromatic hydrocarbons, esters, ketones, alcohols, and heterocyclic alkanes. Enrichment analysis indicated that sesquiterpenoid and triterpenoid biosynthesis, phenylalanine metabolism, and sulfur-related metabolism were the primary pathways involved. Critical odorants such as β-caryophyllene, phenylacetaldehyde, and 1,8-cineole were identified as major contributors. Key genes encoding enzymes central to the biosynthesis of these aromatic compounds were also uncovered. This study provides a molecular foundation for understanding aroma regulation in NHCC and offers practical targets for breeding programs aimed at improving flavor quality.