Genetic mapping of the grapevine veraison locus
Veraison marks the transition from berry growth to berry ripening and is a crucial phenological stage in grapevine (Vitis vinifera): the berries become soft and begin to accumulate sugars, aromatic substances, and, in red cultivars, anthocyanins for pigmentation, while the organic acid levels begin to decrease. These changes determine the potential quality of wine. However, rising global temperatures lead to earlier flowering and ripening, which strongly influence wine quality. Here, we combined genotyping-by-sequencing with a bioinformatics pipeline on ~150 F1 genotypes derived from a cross between the early ripening variety 'Calardis Musqué' and the late-ripening variety 'Villard Blanc'. Starting from 20,410 haplotype-based markers, we generated a high-density genetic map and performed a quantitative trait locus analysis based on phenotypic datasets evaluated over 20 years. Through locus-specific-marker-enrichment and recombinant screening of ~1000 additional genotypes, we refined the originally postulated 5 Mb veraison locus, Ver1, on chromosome 16 to only 112 kb, allowing us to pinpoint the ethylene response factor (ERF) VviERF027 ( VCost.v3 gene ID: Vitvi16g00942, CRIBIv1 gene ID: VIT_16s0100g00400) as veraison candidate gene. Furthermore, the early veraison allele could be traced back to a clonal 'Pinot' variant first mentioned in the 17th century. 'Pinot Precoce Noir' passed this allele over 'Madeleine Royale' to the maternal grandparent 'Bacchus Weiss' and, ultimately, to the maternal parent 'Calardis Musqué'. Our findings are crucial for ripening time control, thereby improving wine quality, and for breeding grapevines adjusted to climate change scenarios that have a major impact on agro-ecosystems in altering crop plant phenology.