Date of Graduation


Document Type





Worthington, Margaret

Committee Member/Reader

Threlfall, Renee

Committee Member/Second Reader

Howard, Luke


The skin color of muscadine grapes (Vitis rotundifolia) is typically classified as black or bronze. A glutathione S-transferase, VrunGST4, has been identified as a candidate gene for berry skin color in muscadine grapes. A molecular marker was developed within VrunGST4 to distinguish between muscadine genotypes (cultivars and selections) with bronze (T:T), heterozygote black (C:T), and homozygote black (C:C) berries. The objectives of this study were to determine whether there was a correlation between berry skin color and total anthocyanin content and to calculate additive and dominance effects of VrunGST4 in determining total anthocyanins in the berries and proanthocyanidin in the seeds of two biparental F1 muscadine populations with the intragenic VrunGST4 marker. No correlation was found between the berry skin color measurements of hue and lightness and anthocyanin content of black-fruited genotypes in either population. However, there was a slight correlation (r = 0.64) between anthocyanin content and chroma in one of the populations. There was no difference in total anthocyanin content of homozygote black (C:C) and heterozygote black (C:T) genotypes in either population, indicating that VrunGST4 had completely dominant gene action. The total anthocyanin content of the berry skins from black-fruited genotypes in one population was approximately four times higher than black-fruited genotypes in our other population. This finding suggests that other genetic loci may contribute to variation in total anthocyanin content in black-fruited muscadine grapes. We also tested total proanthocyanidin content in the seeds of homozygous black, heterozygote black, and homozygous bronze genotypes and found there was no significant difference between the three genotype classes in either population.


muscadine, Vitis rotundifolia, GST, glutathione S-transferase gene, anthocyanin content, anthocyanin, additive and dominance gene effects