GC-MS-Based Volatile Metabolomics and Quantitative Trait Locus Mapping of Aroma Components in 'Muscat Hamburg' Grape.

The muscat aroma of grape is largely determined by terpenoid volatiles. However, its genetic basis in 'Muscat Hamburg' remains unclear. We performed comparative volatile metabolomics between 'Muscat Hamburg' and 'Red Globe' across berry development, identifying 127 differentially abundant metabolites, with upregulated ones enriched in the monoterpenoid pathway. Using an F1 segregating population (264 progeny), we quantified four key monoterpenoids (α-terpineol, linalool, geraniol, and cis-linalool oxide) over two consecutive years. Using a high-density genetic map with 7872 SNP markers generated via SLAF-seq, we detected stable major QTLs for α-terpineol, linalool, and geraniol on LG5, and a novel QTL for cis-linalool oxide on LG14. Expression analysis revealed that the transcript levels of VvDXS and VvGGPPS1 were significantly higher in 'Muscat Hamburg' than in 'Red Globe' at ripening. Heterologous overexpression in tomato enhanced terpenoid aroma accumulation without affecting fruit development. These results indicate that VvDXS and VvGGPPS1 play a crucial role in the formation of the aroma in the 'Muscat Hamburg' variety.