(Adds details throughout on stocks and sectors, updates prices)
TORONTO, March 7 (Reuters) - Canada's main stock index fell on Wednesday, led by materials and auto parts shares, as the resignation of Gary Cohn, top economic adviser to U.S. President Donald Trump, intensified investor worries over a global trade war and its repercussions for the world economy.
* The resignation of Cohn could give free trade skeptics the upper hand in the White House.
* At 9:54 a.m. EST (14:54 GMT), the Toronto Stock Exchange's S&P/TSX composite index fell 17.65 points, or 0.11 percent, to 15,527.54.
* The shares of trade-sensitive auto parts companies lost ground. Magna International Inc fell 0.8 percent to C$67.39.
* The materials group, which includes precious and base metals miners and fertilizer companies, lost 0.4 percent.
* Gold futures fell 0.2 percent to $1,330.6 an ounce, while U.S. crude prices were down 0.7 percent at $62.16 a barrel.
* The energy group dipped 0.1 percent, while industrials declined 0.4 percent as railroad shares fell.
* The TSX posted 1 new 52-week highs and 2 new lows. Six of the index's 10 main groups fell. (Reporting by Fergal Smith Editing by Bernadette Baum)