(Add portfolio manager quotes, details throughout; updates prices)
* TSX dips 3.54 points, or 0.02 percent, to 15,316.02
* Five of the TSX's 10 main groups fall
* Materials and energy groups fall 0.6 percent
* Valeant Pharmaceuticals up 8.0 percent
By Fergal Smith
TORONTO, June 26 (Reuters) - Canada's main stock index edged lower on Monday in cautious trading ahead of the end of the second quarter, as declines in the heavyweight resource and financial groups offset gains for consumer-related shares.
The Toronto Stock Exchange's S&P/TSX composite index fell 3.54 points, or 0.02 percent, to 15,316.02. Trading volume was its lowest in three weeks.
"No one is going to stick their neck out given that it is quarter-end coming up on Friday," said Irwin Michael, portfolio manager at ABC Funds.
"People are a little nervous; little bit of concern out of the (United) States with regard to a flattening yield curve."
The spread between the U.S. two-year and 10-year yield has narrowed to 80 basis points, nearly its smallest gap since September. A flat yield curve could indicate that some investors see a recession ahead.
Gold miners were among the most influential decliners on the index as gold prices sank to near six-week lows. Agnico Eagle Mines Ltd slumped 1.3 percent to C$62.58, while Goldcorp Inc fell 1.2 percent to C$18.07.
The materials group, which includes precious and base metals miners and fertilizer companies, lost 0.6 percent, while gold futures fell 1.0 percent to $1,244.3 an ounce.
The energy group gave back 0.6 percent after rallying on Friday. Suncor Energy Inc fell 1.2 percent to C$38.07 even as oil prices held above last week's seven-month lows.
U.S. crude oil futures settled 37 cents higher at $43.38 a barrel.
Financial stocks, which make up roughly a third of the index's weight, also fell, slipping 0.2 percent as some of the country's top banks lost ground.
Of the index's 10 main groups five ended higher, including the consumer discretionary group, which rose 0.8 percent and the consumer staples group, which rose nearly 1 percent.
Shares of Alimentation Couche-Tard Inc rose 3.6 percent to C$63.62. The company has won U.S. antitrust approval to buy rival CST Brands Inc on condition that it sell up to 71 gas stations in eight states, the Federal Trade Commission said.
Healthcare rallied 2.4 percent, with Valeant Pharmaceuticals International Inc surging 8.0 percent to C$22.61, and reaching its highest since Jan. 10. Shares had jumped last week after billionaire investor John Paulson joined the company's board.
BlackBerry Ltd rebounded 5.7 percent to C$13.59 after sharp losses on Friday following disappointing quarterly results. (Additional reporting by Solarina Ho; Editing by Meredith Mazzilli and Tom Brown)