Examination of molecular mechanism for the color mutation in Chinese wild grapevine (Vitis davidii)

The Chinese wild grapevine, Vitis davidii, is disease resistant, matures late, and is the only Vitis species with white-fruit type native to China, and is ideal for grape breeding programs. To uncover the molecular mechanisms responsible for the V. davidii white-fruit phenotype and the relationship between accessions with white and pigmented fruits, the SSR markers, DNA sequencing and qRT-PCR were used. We found a high coefficient of genetic similarity between the two phenotypes; 12 markers, in particular, revealed that the white-skinned V. davidii "Baiciputao'' evolved from the pigmented "Hunanci''. The MybA1 gene sequence analysis results revealed that "Baiciputao'' harbored only MybA1a at the MybA1 locus, and in "Hunanci'', both MybA1a and MybA1c alleles were detected. This was also linked to grape skin color of the control cultivars, which were Pinot blanc and Pinot noir, Muscat blanc and Muscat rouge. To verify our conclusions, the elementary composition of the anthocyanin profiles of V. davidii and V. vinifera were analyzed using high-performance liquid chromatography and electrospray ionization mass spectrometry (HPLC-ESI-MS/MS), revealing divergent chemical profiles. The main cyanidin derivative in V. davidii was 3-O-glucoside-5-O-glucoside, whereas it was 3-O-glucoside in V. vinifera. The qRT-PCR results indicated that the total anthocyanin content in V. davidii grape skins was not solely determined by UFGT or MYB-related expression levels. These data support the conclusion that the molecular mechanism leading to the white-skinned V. davidii phenotype is the MybA1 gene mutation.