Which is NOT one of the key wine regions of Piemonte?

The selection of Sassicaia DOC as the choice that is not one of the key wine regions of Piemonte is correct. Sassicaia is, in fact, a prestigious wine produced in the Bolgheri region of Tuscany, not in Piemonte. Sassicaia is famed for its high-quality Super Tuscan red wine, primarily made from Cabernet Sauvignon, and has its own distinct identity and terroir associated with the Tuscan coastline.

In contrast, Gavi DOCG, Roero DOCG, and Barbaresco DOCG are all recognized appellations located within the Piemonte region, known for producing a variety of notable wines. Gavi is particularly renowned for its crisp white wines made predominantly from the Cortese grape, while Roero specializes in both red and white wines, often based on Nebbiolo and Arneis, respectively. Barbaresco, one of the most esteemed regions in Piemonte, is celebrated for its elegant reds made from Nebbiolo. Each of these appellations plays a significant role in the overall wine production landscape of Piemonte, making them key regions within that context.