Tazzelenghe grapes on the vine
Tazzelenghe is a red grape found mostly in the Friuli-Venezia Giulia region of northern Italy. In local dialect, the name means "Tongue Cutter" because of its strong tannins and sharp acidity. It is usually blended to tame these characteristics.
Teroldego is a red grape variety exclusive to the Trentino-Alto Adige region of northern Italy. It may be related to Marzemino, but to my knowledge has never been praised in an opera. It is moderately tannic and flavorful, often tasting of blackberries. See I Love Italian Wine and Food - Vino Novello (New Wine) for a review of a Teroldego wine.
Tocai Fruilano
Tocai Fruilano is a the most widely grown white grape variety in the Friuli-Venezia Giulia region of northern Italy. Its wines are pale straw-yellow with an aroma of pears and wildflowers. They also taste of citrus fruits and herbs. In spite of its name, Tocai Fruilano is unrelated to the French (Alsace) Tokay or the Hungarian Tokaji.