TORONTO (Reuters) - Canada's main stock index opened lower on Wednesday, led by declines in energy and financial shares, as concerns about global economic growth and weak U.S. earnings reports hurt investor sentiment. The Toronto Stock Exchange's S&P/TSX composite index was down 39.23 points, or 0.32 percent, at 12,080.69 shortly after the open. (Reporting by John Tilak; Editing by Jeffrey Hodgson)