It is clear that the presence or absence of anthocyanins, the pigments that give color to the grape skins, determines the color of the wine that can be produced, but does this color change have other effects?
In a recent study, in collaboration with other national and European researchers, the VITIGEN group has used white grape variants of the red varieties Garnacha and Tempranillo to study how the presence or absence of red pigments in the skin affects the microclimate of the grape, its composition and even its defenses against pathogens. Both white varieties originated from spontaneous mutations in the respective red variety that resulted in the loss of two essential elements for anthocyanin synthesis, the transcriptional regulatory factors MYBA1 and MYBA2.
Rodríguez-Lorenzo and colleagues show that the presence of anthocyanins in red grapes conditions the internal microclimate of the fruit during ripening, increasing its temperature more than three degrees above that of white grapes. On the other hand, using transcriptomics and metabolomics omics technologies, they detected that the metabolism is modified in many aspects as a consequence of the exposure to light suffered by white grapes and the lack of consumption of anthocyanin precursor molecules. Thus, during ripening, the increased exposure to light causes white grapes to show a higher expression of genes related to the photosynthetic machinery and other light-sensitive genes and to accumulate more precursors of compounds that determine aromatic profiles that can be characteristic of white grapes, such as monoterpenes, norisoprenides, carotenoids, volatile aldehydes derived from fatty acids, or amino acid precursors of phenylpropanoids.
Moreover, the absence of MYBA1 and MYBA2 regulatory elements in white varieties also reduces flavonol trihydroxylation as well as the expression of pathogen defense genes in the berry skin. In addition, white grapes show lower accumulation of alcohols and volatile six-carbon esters and γ-amino butyric acid. Taken together, the results indicate that the reduction in anthocyanin pigment content has important secondary effects on grape composition by altering the internal microenvironment of the berry, which conditions grape and wine aroma and flavor potential, as well as responsiveness to stress conditions.
These results also generate useful information for winemaking, suggesting important differences in composition and aroma between a white wine made from Tempranillo Blanco or Tempranillo Tinto or a rosé wine made from Tempranillo Royo or Tempranillo Tinto.
For more information: https://doi.org/10.1093/jxb/erad223
