More than 80 different grape varieties are authorized for the production of port but until the 1990s few growers had detailed knowledge of the identity of the vines growing in their vineyards. All old vineyards contain a mixture of grapes, often with as many as 20 or 30 different varieties intermingled in the same plot. But research conducted in the 1970s (mostly by Cockburn and Ramos Pinto), identified the best varieties and all new plantings since then have been more orderly. touriga nacional, tinta barroca, touriga franca (often still referred to by its old name Touriga Francesa), Tinta Roriz (Spain’s tempranillo), and tinto cão are the favoured five black-skinned varieties, although varieties such as sousão, tinta amarela, and mourisco find favour with certain growers. gouveio, malvasia Fina, and viosinho are generally considered among the best varieties for white port.