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 × Gewürztraminer 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 Gewürztraminer, 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°C), 120 genotypes from a Riesling × Gewürztraminer 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.
Background and Aims: To analyse the genetic determinants of berry sugar content in grapevine varieties, a method that combined measurements of total soluble solids (TSS) from berries sampled at a fixed stage after veraison with data on the yield and the leaf area was tested.
Methods and Results: Over three seasons, differences in TSS at harvest for Riesling and Gewurztraminer grapes were explained by differences in the veraison dates and in the fruit‐to‐leaf ratios. TSS, yield and leaf area were also evaluated for 120 genotypes, which were progeny from a cross between Riesling and Gewurztraminer. Thermal timescales (degree‐days) proved relevant for describing sugar accumulation in the parent varieties, and when berries were sampled at a fixed heat sum after veraison in the progeny, the genotypic variability of sugar content was considerably reduced compared with the measurements on the same date at the end of the season. A negative relationship between the fruit‐to‐leaf ratio and the sugar content was also detected in the progeny.
Conclusions: The evolution of TSS during berry ripening can be described using thermal timescales. Additionally, information on the yield and the leaf area needs to be integrated to analyse the behaviour of genotypes.
Significance of the Study: A method to characterize the genotypic effect on fruit sugar accumulation after eliminating the contribution of veraison dates and crop load was proposed.
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