Which of the following is not a subregion of Chile's Southern Region?

The Southern Region of Chile is known for its production of high-quality wines, particularly in the valleys south of the country. The three options – Bio Bio, Malleco, and Itata – are indeed recognized as subregions within this area, each contributing unique characteristics and styles to the overall profile of Chilean wine.

Bio Bio is noted for its cooler climate and is associated with varietals such as Pinot Noir and Sauvignon Blanc. Malleco, while lesser-known, also produces cool climate varieties, benefiting from its location and terroir. Itata has a long history of winemaking and is home to old-vine Pais and Muscat of Alexandria, thriving in its unique conditions.

In contrast, Limari is categorized under the more northern part of Chile, specifically the Coquimbo Region. It is famous for its production of exceptional Chardonnay and Syrah due to its proximity to the coast and the unique Mediterranean climate found there. Therefore, it's clear that Limari does not belong to the Southern Region, making it the correct answer in this context.