Discovery of key volatile compound and regulatory gene governing the 'taro-like' aroma in wax gourd ( Benincasa hispida)

The distinctive 'taro-like' aroma in wax gourd has become a crucial flavor characteristic, significantly enhancing its market value. Despite its importance, the volatile compounds responsible for this aroma and their genetic regulatory mechanisms have not been sufficiently studied. Utilizing headspace-gas chromatography-quadrupole time of flight-mass spectrometry (HS-GC-QTOF-MS), this research examined the volatile compounds in wax gourd germplasms with and without the 'taro-like' aroma, identifying 2-acetyl-1-pyrroline (2-AP) as the primary volatile responsible for this aroma. To uncover the genetic basis of this trait, segregating populations and recombinant inbred lines (RILs) were developed from MY-1 x GX-71 germplasms, which exhibit significant differences in aroma expression. Genetic analysis revealed that a single recessive gene governs the 'taro-like' aroma trait in wax gourd. Through bulked segregant analysis sequencing (BSA-seq) and quantitative trait loci (QTL) mapping, the candidate region for this aroma gene was localized to a 285.29 kb interval on Chromosome 2. Further examination of candidate gene expression and sequence variations highlighted the BhBADH gene's critical role in the formation of the 'taro-like' aroma. Additionally, RNA-seq analysis revealed significant enrichment of differentially expressed genes (DEGs) associated with metabolic pathways involved in environmental information processing, which contribute to 2-AP synthesis in wax gourd with a 'taro-like' aroma. Our research provides a theoretical foundation for the molecular breeding to enhance the aroma quality of wax gourd.