The investigation was a collaboration between the Technische Universitaet Muenchen in Bavaria and the JKI Institute for Grapevine Breeding, along the famous Weinstrasse or "wine route" in the Pfalz region. Clues led the researchers to suspect that a difference in a particular phytochemical marker that has long been used to distinguish grape varieties stemmed not from a single gene mutation, but from a double mutation. Furthermore, they revealed, the chromosome bearing the double-mutated gene is one that may also carry a gene responsible for the poor, "musty" aroma of the North American varieties. A complex series of experiments and analyses confirmed this, and ruled out other possible explanations. A detailed description of the methods and results has been published in the Journal of Agricultural and Food Chemistry.
The biochemical process at the crux of the investigation is the production of anthocyanin pigments. Red European Vitis vinifera cultivars produce only pigment compounds such as the one called oenin (malvidin 3-O-glucoside), whereas most other Vitis species and hybrids can produce pigment compounds like malvin (malvidin 3,5-di-O-glucoside) as well. This subtle difference, which has been used to classify wines according to their varietal origin, had been attributed to a particular gene mutation inherited by the European plants. If that was the whole story, however, certain breeding programs might have been expected to turn on malvin production in European varieties, and this had never been observed.
Professor Wilfried Schwab of the Biomolecular Food Technology Department at TUM led the effort to find out what genetic changes would restore malvin-producing enzymatic activity in European varieties wit
|Contact: Patrick Regan|
Technische Universitaet Muenchen