The steep narrow road, high above Portugal's Douro river was half washed out. The car skidded around hairpin curves with vines on one side and no guard-rails on the other, leaving me white-knuckled in the passenger seat.

I had asked to see Touriga Nacional. The name sounds like a football team or an obscure political party, but it's an iconic Portuguese red grape variety, thought by some to rival Cabernet Sauvignon.

Last month, Touriga Nacional was the theme of Portugal's first ever wine conference, held in the northern city of Porto. The country's wine industry heavies were selling the grape as their “national” varietal, hoping to follow the success of Argentina with Malbec and New Zealand with Sauvignon Blanc. US wine writer and blogger Joe Roberts calls it “their great red hope”.

Up to now, the grape has mostly been a star component in the mix of native varieties in the country's famous sweet fortified Ports. Using it alone to make dry reds is recent, and winemakers disagree about whether 100 per cent Touriga can make wines of great quality.

I spent several days at tasting seminars and visits to quintas (wineries) to find out who's right.

In a cavernous auditorium at the Alfandega Congress Center, a former customs building fronting the Douro in Porto, I'd donned earphones for the English translation of the basics. Portugal boasts more than 250 grape varieties and Touriga Nacional accounts for only 2.2 per cent of the country's vines.

Brazil to Australia

The grape's birthplace is the Dao region, but it's now grown in six, from the Douro in the north to the warm Algarve in the south, and no one agrees on which one produces the best wines. This native grape is now planted in Australia, South Africa, Argentina, Spain, California and Brazil.

The seminar sampling of the top dozen 2007 and 2008 examples, selected by an international panel of judges in a pre-conference blind tasting, provoked plenty of heated discussion.

The best all-Touriga Nacional wines have exotic floral aromas (think violets and Earl Grey tea), intense blueberry and chocolatey flavours with an iron tang, and plenty of tannin so they can age. But sipping through the winning line-up from six regions, I was mostly underwhelmed.

Some lacked concentration and complexity and tasted like big ripe reds with a hole in the middle of the taste. The 2008 Munda was loaded with oak. Two from southern regions had that hot finish that screams high-alcohol. My favourites were from the Douro and the Dao regions: deep-coloured, structured 2008 Quinta do Vallado ($40), well-balanced, powerful 2008 Churchill's Estates ($25), and the vibrant, earthy 2008 Quinta das Marias ($30).

‘The Winner Is...'

The winners had been announced the previous evening at a gala dinner at the grand 19th century Palacio da Bolsa, once Porto's stock exchange. As we sipped from a choice of 30 Tourigas under a vast metal-and-glass dome in the 32-meter-high Hall of Nations room, names of the winners were drawn from white envelopes, then flashed on a screen. It was like the Oscars minus the jokes.

Attendees grumbled that other labels regarded as the best - like Quinta do Crasto - weren't on the list, and some claimed they showed why Touriga Nacional needed to be blended with other grapes to make great wine.

Touriga Blend

So I headed to Quinta do Crasto and a few other estates far up the Douro, where the steep terraced vineyards produce the grapes for Port, and increasingly, for table wines.

Historic Quinta de Roriz, owned by a partnership of the Symington family of Port fame and Bruno Prats, former proprietor of Bordeaux's Chateau Cos d'Estournel, lies close to the river down a vertigo-inducing road from the highest vines.

Here, Prat & Symington makes rich, smooth, layered Chryseia ($50), a 50/50 blend of Touriga Nacional and Touriga Franca.

“Nacional gives structure and mineral notes, Franca gives freshness, bright red fruit, and floral aromas,” says the winemaker, who let me try barrel samples of each. The blend was definitely more complex.

At Quinta do Crasto, Miguel Roquette, whose family owns the quinta, points out to old twisted Touriga Nacional vines backed by a setting sun and explains they made the first 100 per cent Touriga in the Douro in 1995. The 2009 tank sample is savoury, rich, spicy, chocolatey and very pure. “You need old vines for it to be great on its own,” he says. Just like Cabernet, Touriga Nacional can make wonderful wines on its own (think Napa Valley) but only in the very best sites. Often it's better as the backbone of splendid blends (think Bordeaux).

I'd hate to see Portuguese winemakers fixate on a single role for Touriga Nacional - or forget their other grapes.