Synonym or breeding number (also GM 8331-1) for the grape variety Allegro; see there.
The red grape variety (also Geisenheim 8331-1) is an interspecific new variety between Chancellor (Seibel 7053) x Rondo. It contains genes from Vitis aestivalis, Vitis amurensis, Vitis labrusca, Vitis rupestris and Vitis...
The glossary is a monumental achievement and one of the most important contributions to wine knowledge. Of all the encyclopaedias I use on the subject of wine, it is by far the most important. That was the case ten years ago and it hasn't changed since.
Andreas Essl
Autor, Modena