A bud sport is a somatic mutation in shoot cells of perennial fruits. We report here the molecular characterization of a white color mutation in Pinot gris. The Pinot gris bud sport neither accumulated anthocyanins in the skin nor expressed UDP glucose-flavonoid 3-o-glucosyl transferase. Genomic analysis with cleaved amplified polymorphic sequence markers located on each side of the VvmybA gene cluster of color loci demonstrated that the bud sport was heterozygous with one red allele and two white alleles. However, the red allele had a large deletion in the color locus, resulting in white-skinned berries. In addition, the Pinot gris bud sport showed a triallelic profile at the locus based on genotyping with a microsatellite DNA marker, indicating that genetically different cell layers, L1 and L2, coexisted in the berries. Taken together, we conclude that the color mutation in this Pinot gris bud sport might have arisen from a large deletion in the color locus of the red allele of L1 cells and not from L1 and L2 cell layer arrangements. These findings and further studies of a Pinot gris bud sport are expected to provide new information on the genetic mechanisms underlying white-fruited grapevines and improve our understanding of grape domestication.
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