The Keys to Color and Variations in the Gene
Color is a vitally important quality trait of table, juice, and wine grapes that has been linked to health promoting antioxidant content. The genetics behind this trait is something that until recently has been poorly understood. Working with a geneticist of INRA (Institut National de la Recherche Agronomique) in Montpellier, France, GGRU geneticists expanded on independent 2004 research in Japan that identified a genetic mutation known as Gret1 as responsible for white-skinned grapes.
That study showed that Gret1’s interaction with VvmybA1, a gene found in all V. vinifera grapes, was key to white fruit color. Gret1 is a transposable element, also known as a ‘jumping gene’ because it is a member of a class of DNA that can move around within the genome. Grapes, being diploid organisms, have two copies of every gene. When Gret1 is present in both copies of VvmybA1, the grapevine will bear white fruit.
In addition to verifying those findings, the Geneva group studied grape cultivars’ VvmybA1 genes for clues that hint at what promotes different-colored grapes. Variations of this gene, spurred by mutation and movements of transposable elements, cause a large proportion of color variation in modern grape cultivars. In this case, when Gret1 ‘visits’ and then leaves, it slightly alters the surrounding DNA. These alterations then create additional variation in VvmybA1, which in turn can lead to variation in fruit color.
This finding may help improve efficiency in breeding new grape cultivars for specific colors, as well as the intensity and color stability of juices and wines. It may also lead to better understanding of how environment and management practices affect grape color and quality, and of the relationships between fruit color and healthy compounds.