Legh Knowles, a leader in the wine industry and former trumpeter for the Glenn Miller Orchestra, has died following a long illness. He was 78.Knowles, who died Aug. 15 in a convalescent home in Napa, was best known in his later years as chairman of Beaulieu Vineyards in the Napa Valley and as a spokesman for the wine industry, where his quick wit, resonant voice and lack of pretense made him immediately successful. But in earlier years, he made his fame as a trumpeter with the Glenn Miller Orchestra. Knowles joined Miller in 1939, the same year that the Miller Orchestra hit the top of the charts, where it would remain until Miller’s death in 1944. He also performed with Charlie Spivak, Red Norvo and Mildred Bailey. Knowles joined the Army Air Corps in 1941. Following the war, Knowles returned to the United States and became a member of the Wine Advisory Board in Washington, which in those days was a promotional arm for the California wine industry. He later joined the Ernest and Julio Gallo empire in Modesto as a salesman. But in 1962, frustrated with Gallo’s reluctance to get into the premium wine market, he ventured out to Beaulieu, known for its top-of-the-line cabernets, to be national sales manager. Knowles also was known for doing his own radio commercials, down-to-earth pleas to listeners to enjoy the simple virtues of a good glass of wine. During his 27 years with Beaulieu Vineyards, where he worked as both president and chairman, Knowles eschewed wine’s snob appeal, urging consumers instead to choose wines that appealed to individual tastes rather than those chatted up by so-called wine experts. He retired nearly a decade ago as chairman of Beaulieu. Knowles is survived by his wife Margaret, a daughter, two grandchildren, a sister and a brother.