Genome-Wide Association Study Identifies Candidate Genes Regulating Berry Color in Grape (Vitis vinifera L.)

Berry color is a critical determinant of grape quality and market value. While the genetic basis of skin color has been extensively studied, the regulatory network controlling flesh coloration remains largely uncharacterized. To systematically dissect the independent genetic architectures underlying these traits, we performed a genome-wide association study (GWAS) on 130 grape accessions, integrated with spatiotemporal expression profiling, subcellular localization, and functional validation. Our analysis revealed distinct genetic loci for skin and flesh color, confirming their independent regulation. For skin color, GWAS robustly validated VvMYBA2 as a major locus, explaining up to 51.5% of the phenotypic variance. More importantly, for flesh color, we identified and prioritized VvF3′M (Flavonoid 3′-monooxygenase) as a key candidate gene. Heterologous overexpression of VvF3′M in tobacco resulted in a profound 13.5-fold increase in anthocyanin content, suggesting its potential role as a rate-limiting enzyme in flesh pigmentation. Intriguingly, VvF3′M-overexpressing plants also exhibited a significant increase in flower number, suggesting a novel role beyond pigment biosynthesis. This study provides a comprehensive genetic and functional framework for understanding berry coloration, identifies VvF3′M as a prime target for breeding red-fleshed grapes, and reveals unexpected crosstalk between color metabolism and reproductive development.