The exact origin of this white grape variety is unknown. Synonyms are Krainfranke and Philipp Cuntzrebe. You mustn't go with that Sylvaner be confused, which was also called Grünfränkisch in the past. According to the period from 2014 to 2016 DNA analysis (Dr. Erika Maul dated JKI ) comes from a presumably natural cross between Auxerrois x Kövidinka, It is a very old variety that has already been considered extinct. It was awarded in 2009 by graduate biologist Andreas Young rediscovered. This means that from a 300-year-old variety description that can not be derived Riesling, but very probably the actual Franconian grape variety Liebfraumilch was. Already in the 16th century the Grünfränkisch was used for the south palatinate mentioned. The history of this grape goes back to antiquity and found her home on Northern Hungary on Rhine, It was one of the so-called Frankish, so qualitatively "better" varieties.
Source (Andreas Jung) and picture: Historical grape varieties