* TSX down 56.72 points, or 0.46 pct, at 12,362.27 * All 10 sectors lower in broad decline By Claire Sibonney TORONTO, Oct 9 (Reuters) - Canada's main stock index opened lower on Tuesday, tracking a decline in world markets on caution about the upcoming earnings season and the prospects for global growth. All 10 of the index's sectors fell amid a wave of negative signals, including a report from the International Monetary Fund that said the global economic slowdown is worsening. The IMF cut its growth forecasts for the second time since April. Europe also kept investors on edge as uncertainty about when Spain will apply for a bailout worried markets and new concerns about Greece's direction weighed on sentiment. Commodity and financial shares were among the hardest hit. Barrick Gold fell 1.4 percent to C$40.54, Suncor Energy was down 0.8 percent at C$32.73, and Bank of Nova Scotia lost 0.5 percent to C$53.80. Bruce Latimer, trader at Dundee Securities, said volumes were light at the start of a holiday-shortened week as Canadian markets were closed on Monday for Thanksgiving Day, while U.S. government offices and some financial markets were shut for the Columbus Day holiday. "They're just playing at little catch-up here to the U.S. market right now. It's actually kind of a quiet opening here," he said. At 10:15 a.m. (1415 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 56.72 points, or 0.46 percent, at 12,362.27. The U.S. quarterly earnings season will get under way later in the day when Dow component Alcoa Inc reports after the market close. Analysts forecast third-quarter earnings of S&P 500 companies will drop 2.3 percent from the year-before quarter, according to Thomson Reuters data, which would be the first drop in U.S. quarterly earnings in three years.