Genetic variability of descriptors for grapevine berry acidity in Riesling, Gewurztraminer and their progeny

Background and Aims: The acidity of harvested grapevine berries is likely to decrease in the future because of increasing temperature during grape ripening. The aim of the study was to evaluate the genetic variability of berry acidity descriptors in progeny from a Riesling x Gewurztraminer cross. Methods and Results: The ripening process for the parent cultivars was monitored over three growing seasons; berries from Riesling had a higher tartaric acid concentration than that from Gewurztraminer, and a similar difference was observed for malic acid. A statistical model describing the decline in malic acid concentration over time was fitted to the data. With this model, the parameter that best characterised the two genotypes was the asymptotic minimum value of malic acid concentration per g of berry dry matter. In addition, the rate of decrease of malic acid was constant across years when thermal-time scales were used. Using samples of green berries at veraison and samples picked 230 degree days after veraison (mean temperature, base 10 degrees C), 120 genotypes from a Riesling x Gewurztraminer progeny were compared over 3 years in the vineyard and segregations for all the berry acidity descriptors were described. Conclusions: A significant genotypic variability was observed for the concentration of malic and tartaric acids but also for the estimated cationic content of the berries for the same developmental stage. No genotypes, however, were detected, with a concentration of total malic and tartaric acid significantly higher than that of Riesling. Significance of the Study: These results show that berry acidity descriptors are heritable traits that can be manipulated in breeding programs.