Which grape variety is not used in the production of Retsina?

Retsina is a traditional Greek wine, primarily known for its distinctive resin flavor, which comes from the use of pine resin during fermentation. The grape varieties used in the production of Retsina are typically those that thrive in the Mediterranean climate and can balance the resin's strong flavor.

Savatiano and Roditis are the two most commonly used grape varieties for making Retsina. Savatiano is the dominant grape, preferred for its ability to blend well with the resin and produce a wine with good freshness and acidity. Roditis adds to the aromatic profile and also complements the characteristics of Savatiano.

Malagousia is another white grape variety that may not be traditionally associated with Retsina but is sometimes used in modern adaptations. Its profile can add another layer of complexity to the wine, though it is not as common as the first two.

Xinomavro, on the other hand, is a red grape variety primarily used to produce red wines in Greece. It is known for its high acidity and tannins, which makes it unsuitable for Retsina's white wine production. Thus, Xinomavro is the grape variety not used in the production of Retsina, confirming that it is the correct answer to this question