Allelic variation in the VvMYBA1 and VvMYBA2 domestication genes in natural grapevine populations (Vitis vinifera subsp. sylvestris)

Grape skin color is among the most important qualitative traits on which selection is based in wine and table grape breeding programmes. Skin color is determined by the quantity and composition of anthocyanins. In prior work on cultivated forms, it was shown that polymorphisms in the grape transcription factor family VvMYBA are responsible for anthocyanin content variation in the berries of cultivated grapevine (Vitis vinifera subsp. vinifera). Wild grapevine (V. vinifera subsp. sylvestris) is the ancestor of the cultivated V. vinifera subsp. sativa and has black-colored berries. The purpose of this study was to determine how the VvmybA1 and VvmybA2 polymorphisms emerged and affected the genetic diversity of wild grapevines in the Mediterranean basin by examining samples from the Iberian Peninsula, Italian Peninsula and Caucasian region. Our observations provide evidence that variation in the two transcriptional regulators generated a novel allele series via length polymorphisms in VvmybA1 and a point mutation in VvmybA2, which is lacking in cultivated grapevine. Further, correlation was detected between allele composition and anthocyanin contents. According to polymorphisms in both VvMYBA genes at the color locus, we were able to identify several haplotypes. The most ancestral haplotype (HapN) was found in wild grapevine in the western Mediterranean region and corresponded to wine grape cultivars, whereas recent haplotypes were detected in eastern regions. These eastern zones showed the most diverse haplotypes, which appeared in table cultivars where intense breeding practices may have replaced the original haplotype diversity. These findings provide information about the evolution of grapes since their domestication and have direct implications for wine quality.