‘Zhengmei’: A new early-ripening table grape

Introduction: As a result of natural hybridization and human selection over centuries, the grape berry skin colour has become greatly diversified. The colour of grape skins is determined by the accumulation of anthocyanins (HARBONE et al. 2000). Anthocyanin content is a trait of major interest in Vitis vinifera L. They have very important role in wine and grape industry, confer colour and contribute to other sensory characteristics (BOSS et al. 1996). Molecular analyses of structural genes involved in the anthocyanin biosynthetic pathway showed that expression of the UDP glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene is a critical point in the control of berry colour (KOBAYASHI et al. 2001). It was shown that Myb-related gene, VvMybA1, regulates anthocyanin biosynthesis in grapes via UFGT gene expression (KOBAYASHI et al. 2004, 2005) and the colouring of grape skin depends on the genotype of VvMybA1 (LIJAVETZKY et al. 2006, AZUMA et al. 2007). Recently, it has been shown that the presence of Gret1, a Ty3–gypsy-type retrotransposon, in the promoter region of VvMybA1 gene, is associated with white-berry cultivars when present in a homozygous state (KOBAYASHI et al. 2004). Coloured cultivars hold at least one allele at the VvMybA1 locus not containing this large insertion: VvMybA1b or VvMybA1c (KOBAYASHI et al. 2004, AZUMA et al. 2007, YAKUSHIJI et al. 2006). It was revealed that the VvMybA1b and VvMybA1c alleles are functional. The VvMybA1b allele has a single long terminal repeat (LTR) of Gret1 in the 5 flanking region near the coding region of VvMybA1 gene (AZUMA et al. 2007). VvMybA1c, the wild type allele, is the original sequence of VvMybA1 gene before the insertion of Gret1 (YAKUSHIJI et al. 2006). In most examined white-skinned grapes, the colour locus is homozygous for VvMybA1a, whereas the genotype of colour skinned berries are heterozygous (VvMybA1a/VvMybA1b or VvMybA1a/ VvMybA1c) or are homozygous (VvMybA1c) (AZUMA et al. 2008). Due to the lack of data for Armenian grapevines, the present study has the objective to analyze the role of VvmybA1 gene in berry color variation. In order to ascertain the existent allelic composition for this gene and its association with berry color variation, thirty autochthonous Armenian grapevine cultivars were analyzed.