(MarketWatch) — They call it “moscato madness” around the headquarters of E. & J. Gallo Winery. And for good reason. Gallo is selling at least six times the amount of sweet-tasting Moscato wine than just three years ago. Moscato, a take on its Muscat origins, is the fastest-growing varietal in the U.S. wine business, making it a sales boom for Sutter Home, Beringer and Robert Mondavi’s STZ +0.15% Woodbridge label.