I found myself wondering why this might be the case. The more I thought about it, the more I realized that I actually knew very little about Portugal's history as a nation, and it turns out that this history is pretty important in understanding the current state of the Portuguese wine industry. As mentioned in a few of my posts on the Georgian wine industry and the Romanian wine industry, the political climate within a given country can have at least as much of an impact on the wine industry as the natural climate can, and is often much more important. Given Portugal's historical standing as one of the great European powers in the world and their current standing as one of the great developed nations of western Europe, it's easy to forget that there was a period of time in between where things didn't look quite so good.
In the 15th and 16th Centuries, Portugal was one of the great nations of the world. Many of history's great explorers, like Vasco da Gama, were Portuguese and Portugal used its navy to become an active colonial power, claiming territories in places as geographically disparate as Brazil and Taiwan. Their empire faltered and fell apart, as all of the great colonial empires did, throughout the next few centuries. The modern history of Portugal can perhaps be said to have started in 1908 with the assassination of King Dom Carlos I and his heir apparent. Manuel II was pronounced King, but his reign was shortlived. The military overthrew the monarchy for good on October 5, 1910, and the Portuguese First Republic was founded. This republican government was able to stay in power until 1926 when the military stepped in and overthrew it, establishing the Ditadura Nacional, or National Dictatorship. This was followed in 1933 by the Estada Novo, or Second Republic, which was implemented by António Salazar who remained in power until 1968.
Salazar reorganized both the government and the economy based on the theory of corporatism (which you'll just have to read about here, if you're interested, as I'm not sure I can accurately summarize it). The wine industry was part of this reorganization as well and many co-operatives were set up for the production of wine. The State had a large degree of control over the industry, which is almost always a recipe for disaster for the production of quality wines as the State's interests are almost always profit-oriented rather than quality-oriented. The overall quality of Portuguese wines began to fall and that fact coupled with the fact that many countries weren't comfortable dealing with authoritarian regimes led to the isolation of Portugal politically and culturally from the rest of Europe and also served to isolate the Portuguese wine industry as well.
The Portuguese government was once again overthrown by its military in 1974 during the Carnation Revolution. This revolution started the process of independence for Portugal's overseas colonies and paved the way for a democratic government to come into power. The new Portuguese constitution was ratified in 1976 and Portugal joined the EU in 1986. Portugal has made tremendous strides in a very short period of time in a multitude of different economic theaters, but the resurrection of their wine industry in a mere 40 years has been truly remarkable. Their wines have dramatically increased in quality and are distributed in greater and greater numbers to the US and to other countries throughout the world.
One of the consequences of the state-run wine industry was that there wasn't much research conducted on the history of Portugal's wealth of native grapes. When wine is treated solely as a commercial product, the details of the grapes themselves are of little consequence and there's virtually no reason to devote any time or resources to tracking or tracing their particular histories or characteristics. There has been a bit of renewed inquiry lately, but most of the studies that I've found have been focused on testing large collections of genetic material to eliminate synonymies across different regions, which are interesting to some extent but ultimately don't really offer any information about the grapes that don't have any alter egos in other areas. The other issue is that, historically, Portugal has mostly produced fortified and sweet wines for export and their turn to making dry table wines is a very recent phenomenon. There may be a lack of historical information about many of these grapes simply because they are only recently being used in dry table wines meant for export.
All of which is to say that there's very little information available about the Antão Vaz grape. It is one of the better regarded native Portuguese vines, but is grown almost exclusively in the Vidigueira region of Alentejano, which is located about halfway in between the Atlantic Ocean and the Spanish border in the southern half of Portugal. The grapes are large with thick skins and their clusters are somewhat loosely packed, all of which are helpful in combating fungal infections of the vine. It is somewhat similar to Chardonnay in that it makes crisp, lively wines with nice acidity if picked early but can also make bigger more alcoholic wines that are suitable for barrel aging if left on the vine a bit longer. It is somewhat frequently made into a varietal wine, though it is also occasionally blended with other local grapes like Arinto.
