Structural dynamics at the berry colour locus in Vitis vinifera L. somatic variants

This study aims at the molecular characterization of somatic variants for the berry skin colour, taking advantage of a layer-specific approach and of the knowledge of the genomic sequence along the chromosome 2. The plant material consisted of 38 individuals belonging to 14 V. vinifera cultivars (cépage), encompassing the group A (‘Calitor’, ‘Canaiolo’, ‘Cariñena’, ‘Merlot’, ‘Rondinella’, ‘Grenache’ and ‘Tempranillo’), colourless variants from coloured wild-type, and the group B (‘Baresana’, ‘Chasselas’, ‘Italia’, ‘Malvasia di Candia aromatica’, ‘Moscato bianco’, ‘Sauvignon’ and ‘Sultanina’), coloured variants from non-coloured wild-type. A set of 11 reference SSR markers was used to confirm the varietal identification. In order to perform the genetic characterization at the berry colour locus, 10 SSR markers, 6 SNP regions, and 1 SCAR marker (Gret1) distributed along the chromosome 2 were analysed. The major findings of this study revealed a structural dynamics along the chromosome 2 both at inter- and intra-varietal level within the group A. In fact, a deletion of different extent and position was detected in the colourless variants at the inner layer level. Within group B, instead, the coloured variants could be distinguished mostly for the partial Gret1 retrotransposon excision from the VvMybA1 promoter. In conclusion, this study allows the discrimination of somatic variants and suggests the occurrence of different evolutionary models both among and within grapevine cultivars