Living in the heart of Sonoma County wine country gives me direct access to winemakers, occasionally in grocery stores or parking lots. Two weeks ago, I bumped into a friend, a winemaker for a small winery who bemoaned that prices for merlot grapes were rising a lot higher than he had anticipated, which made his job more difficult. His winery’s cabernet sauvignon has always been made with about 20 percent merlot. Since merlot prices are always lower than he has paid for cabernet, the winery could continue to keep the cabernet sauvignon priced reasonably. But the way prices for merlot were rising, he said, he had only two choices: either raise the price of the cabernet or use a lot less merlot and replace it with lower-caliber grapes, which would undoubtedly change the style of wine. Neither choice was ideal. The story of California merlot goes all the way back …