Final answer:
The most important grape variety in Rioja is the Tempranillo, which is known for its versatility and reflection of the region's terroir. It produces wines with a complex balance of fruit and earthiness. Other grape varieties like Garnacha, Mazuelo, and Graciano are also grown in Rioja but Tempranillo remains the principal variety.
Step-by-step explanation:
The most important grape variety in Rioja, which is a significant wine region in Spain, is not Pedro Ximénez or Trebbiano. Rather, it is the Tempranillo grape that is considered the backbone of Rioja wines. This grape variety is highly valued for its versatility and its ability to reflect the terroir of the Rioja region, providing a balance of fruit and earthiness in the wines it produces. Tempranillo grapes tend to produce wines that are ruby in color, with aromas and flavors of berries, plum, tobacco, vanilla, leather, and herb, these flavors becoming more pronounced and complex as the wine ages. In Rioja, these wines can range from lively and fresh to deeply complex and age-worthy when produced in the form of Rioja Gran Reserva.
In addition to Tempranillo, other grape varietals such as Garnacha (Grenache), Mazuelo (Carignan), and Graciano are also planted in Rioja, but none are as prominent or as esteemed as Tempranillo. Although Pedro Ximénez and Trebbiano are indeed grape varieties, they do not hold the same significance in Rioja. Pedro Ximénez is more commonly associated with the sweet wines of Jerez, while Trebbiano is more commonly found in Italy and France under the name Ugni Blanc.