HEALDSBURG, Calif. — This was no typical tour of the Sonoma County wine country, and these were no typical tourists.

As a Santa Rosa Junior College instructor explained trellising systems and drip irrigation, a group of young Japanese liquor retailers and sommeliers--or wine stewards--traipsed along behind him through dusty vineyards scattered over the hills and dales of Sonoma County.

Between jotting notes and snapping pictures of grapevines, they stopped occasionally to sample a glass of Chardonnay or Pinot Noir.

The viticulture lesson \o7 al fresco \f7 was part of a campaign by California vintners to drum up more business in Japan, where beer is the overwhelming drink of choice and wine captures only a tiny fraction of the alcoholic beverage market.

"It's time that young Japanese sommeliers start to understand California wines," said Linda R. Johnson, executive director of the Sonoma County Wineries Assn. in Santa Rosa. "Many of the older ones are Francophiles."

The idea for the tour grew out of an April visit to Japan by 19 Sonoma County wineries, including Glen Ellen, Alexander Valley, Kenwood and Grand Cru. During four days in Tokyo and Kobe, they held seminars and tastings for the Japanese Sommelier Assn. Members of that prestigious group determine what wines are served in Japan's fine hotels and restaurants.

Akio Hayashi, a sommelier and wine consultant to Western-style restaurants in Tokyo such as Spago, Tony Roma's and Hard Rock Cafe, decided to organize a weeklong U.S. trip for Japanese who deal in the wine trade. Six men and women, ranging from 19 to 32, signed up. Although wineries provided overnight accommodations and most meals, the visitors covered their own travel costs.

That, Hayashi noted, was significant. In the past, the costs of such trips have usually been borne by the Wine Institute, a trade group, or by vintners. The willingness of the individuals or their employers to pay for plane fare, he said, is a sign that interest in California premium varietals such as Chardonnay, Cabernet Sauvignon and Sauvignon Blanc is growing, partly because of stepped-up travel to the West Coast by Japanese.

"When people get to know it more, they will sell more of it in Japan," said Hayashi, a veteran of several wine-country tours in France and California. The key, he added, is "understanding" the wine.

Masao Suzuki was impressed by the Sonoma County wine industry's "strong spirit" and the willingness to discuss grape growing and winemaking techniques.