* TSX down 15.87 points, or 0.1 percent, to 15,144.55
* Seven of the TSX's 10 main groups were down
* Consumer staples down 2.3 percent
* Consumer discretionary down 1.2 percent
By Solarina Ho
TORONTO, June 16 (Reuters) - Canada's main stock index fell on Friday, as shares of grocers and other consumer staple companies took a beating on news that internet retail company Amazon.com Inc was buying Whole Foods Market Inc .
Amazon announced before markets opened that it was purchasing the U.S. organic supermarket chain for $13.7 billion, including debt, marking its biggest foray into the brick-and-mortar retail sector.
The Canadian consumer staples sector tumbled as much as 3.36 percent in its sharpest fall since October 2008 before it pared losses to 2.3 percent.
The country's largest grocery chain operators all declined sharply.
Loblaw Companies Ltd, which has more than 2,300 corporate, franchised and associate-owned grocery stores and pharmacies across Canada, was down 3.8 percent to C$72.61, after falling as much as 5.8 percent.
Empire Company Ltd, which has about 1,500 Canadian stores operating under banners including Sobeys and FreshCo, fell 3.3 percent to C$18.80. Metro Inc, which operates some 600 supermarkets in Quebec and Ontario, fell 4.1 percent to C$42.64.
At 11:05 a.m. ET (1505 GMT), the Toronto Stock Exchange's S&P/TSX composite index fell 15.87 points, or 0.1 percent, to 15,144.55. Of the index's 10 main groups, seven lost ground.
Consumer discretionary shares also retreated sharply, declining 1.2 percent, with Magna International Inc taking a 3.8 percent hit to trade at C$57.73.
Dollarama Inc slid 1.5 percent to C$121.45, while Canadian Tire Corp fell 1.7 percent to C$146.90.
The materials group, which includes precious and base metals miners and fertilizer companies, lost 0.6 percent.
Teck Resources Ltd fell 5.2 percent to C$20.46, extending losses from the previous session after the miner said it was lowering its forecast of the average realized price for its steelmaking coal in the second quarter. Several analysts cut its target price on the news.
The energy group was one of the few gainers, climbing 0.6 percent on the back of firmer crude oil prices. U.S. crude prices were up 0.4 percent to $44.64 a barrel.
Pipeline operator Enbridge Inc rose 1.5 percent to C$51.05.
Declining issues outnumbered advancing ones on the TSX by 136 to 105, for a 1.30-to-1 ratio on the downside. (Reporting by Solarina Ho; Editing by W Simon)