A mutation in CmoBADH results in the production of 2-acetyl-1-pyrroline, conferring a 'taro-like' aroma in Cucurbita moschata.

Key message: We mapped and cloned gene Cmobadh controlling the 'taro-like' aroma in pumpkin, enabling MAS-driven breeding of 'taro-like' aroma cultivars through utilizing the variant-derived molecular marker. 'Taro-like' aroma is a pleasant flavor characteristic of pumpkin. However, the genetic and molecular basis underlying the valuable agronomic trait remains unclear. In this study, an F₂ population was derived from a cross between two pumpkin accessions, including accession NO. 44 with 'taro-like' aroma and accession NO. 45 without 'taro-like' aroma. Genetic analysis revealed that 'taro-like' aroma was controlled by a single recessive gene. Further bulked segregant analysis and polymorphic markers mapped the locus to a 23.3-kb region on chromosome 10. The genomic assembly of NO. 44, generated using third-generation sequencing technology supplemented with Sanger sequencing, revealed a structural variation consisting of a 4,591-bp insertion within the mapped region. The variation is located within an intron of CmoCh10G001620, thereby disrupting its transcription. CmoCh10G001620 encodes betaine aldehyde dehydrogenase and functions as the candidate gene controlling the production of the 'taro-like' aroma compound 2-acetyl-1-pyrroline. Further analysis of 40 plant accessions revealed that the insertion was present in all 10 accessions exhibiting a 'taro-like' aroma, but absent in the other 30 accessions without the special aroma. These findings conclusively identified CmoCh10G001620 as a key gene that regulates 'taro-like' aroma. In addition, molecular marker-assisted selection was successfully used to develop new fragrant pumpkin cultivars that are distinct from conventional pumpkins, through targeted breeding strategies. Our results provide a theoretical foundation for further investigation into the mechanism underlying the 'taro-like' aroma, and may assist in the selection and breeding of pumpkin varieties exhibiting the trait.