Which grape variety is often mistaken for Carmenere before genetic testing?

The grape variety that is often mistaken for Carmenere before genetic testing is Merlot. This confusion arises primarily because both Carmenere and Merlot share similar physical characteristics, particularly when it comes to the appearance of leaves and grapes. Additionally, Carmenere, which is originally from Bordeaux and also grown in various regions, was formerly thought to be a clone of Merlot in places like Chile, where it was extensively planted without proper identification.

Genetic testing has since established the distinct identity of Carmenere, but prior to these advancements, the close proximity in flavor profiles and growing habits led to frequent misidentification.

While Cabernet Sauvignon, Syrah, and Malbec are also significant grape varieties with their own unique qualities, they do not have the same level of similarity in appearance and characteristics to Carmenere as Merlot does. Thus, when focusing on how often confusion occurred historically, especially in regions where Carmenere became associated with Merlot, it is clear why Merlot is the most often mistaken variety.