(Updates official closing numbers, adds details, quotes)
TORONTO, April 29 (Reuters) - Retreating commodities helped knock 260 points off the Toronto Stock Exchange's main index on Tuesday, as it was dragged lower by sinking resource shares.
A selloff in oil and gold, key underlying commodities for the resource-laden Toronto benchmark, sent the materials and energy sectors tumbling 4.8 percent and 2.9 percent respectively.
"Today is a reminder that commodities can impact the TSX to the downside as well as the upside," said Elvis Picardo, investment strategist at Northern Securities Inc in Vancouver.
"So far this year, they've really been propping the index up nicely, while the U.S. indexes have been sliding all along, but today it's the reverse."
The S&P/TSX composite index .GSPTSE closed down 260.25 points, or 1.85 percent, at 13,825.60 with all but two of its 10 main sectors pointing south.
Gildan Activewear (GIL.TO) was among the biggest drags on the index after the T-shirt maker cut its full year and second-quarter earnings per share guidance. Gildan plummeted C$11.08, or 30.6 percent, to C$25.18.
Potash Corp of Saskatchewan (POT.TO) pulled the index deeper under water, as the fertilizer company skidded C$12.33, or 6.3 percent, to C$183.27. Its stock had seen a recent steep runup in the wake of soaring demand and prices for potash.
On the upside, Rogers Communications (RCIb.TO) climbed C$1.56, or 3.6 percent, to C$44.46 after it said its first-quarter profit more than doubled and it announced a deal with Apple (AAPL.O) to launch the iPhone in Canada this year.
Rogers' advance helped propel the telecoms sector up 0.8 percent. The only other sector in positive territory was the tech group, which rose 1.8 percent. ($1=$1.01 Canadian) (Reporting by Leah Schnurr; editing by Rob Wilson)