By Johan Burger
In South Africa, as in other grape-growing areas, there is a newfound interest in old vines and vineyards, and the exceptional wines made from them. Wines produced from older vines are generally accepted as having more depth and complexity than those produced from younger vineyards, and this term is used on wine labels to indicate a wine of high quality. Nonetheless, no formal classification exists to classify a vine as an “old vine”, and it largely depends on the history of vineyards and winemaking in the area. For example, in old-world wine production areas many vineyards in excess of 100 years may exist. In contrast, in a new world growing area, a vine of 50 years might be considered old. In South Africa, the economic life of a vineyard is an average of 20 to 25 years, and vines are generally considered to be old when they reach 35 years.
Describing wines made from old vines as having more depth and character is subjective, and to our knowledge no scientific research has been done to prove which compounds differ between young- and old-vine wines. Changes in gene expression and hormone levels play a role in initiating and controlling ripening and influence flavour and aroma compounds accumulating in the berry. Still, it is unknown to what extent gene expression levels differ between young and old vines.
To study this distinctive old-vine character, gene expression profiling of both berries and leaves from young and old Pinotage vines at harvest, were performed. Vine material was sampled from a commercial Pinotage vineyard where young and old vines are inter-planted. This data was used to form an overall picture of gene expression in leaves and berries of Pinotage vines.
Differential gene expression between young and old vines was studied, and the involvement of these genes in fruit ripening, discussed. In addition, we used a metagenomic approach to compare fungal, bacterial and viral populations in young versus old plants, in order to understand the possible role of these microbiomes in wine quality.
Researcher: Johan Burger
This project is funded by the Pinotage Association