Which of the following is a commercially significant white grape variety?

Pinot Grigio is indeed a commercially significant white grape variety. It is widely cultivated and has a significant presence in the wine market, particularly in regions like Italy, where it is known for producing light, crisp, and refreshing wines that are popular with consumers. The grape can also be found in other wine-producing countries, and its versatility allows for a range of styles from dry to sweet, making it appealing to a broad audience. These characteristics contribute to its importance and popularity in the wine industry, leading to substantial production and sales.

The other grape varieties mentioned—Malbec, Tempranillo, and Cabernet Sauvignon—are primarily red wine grape varieties and are known for their significance in red wine production. While they are important and commercially successful, they do not fall into the category of white grape varieties.