March 11 (Reuters) - Canada’s main stock index opened higher on Thursday as energy and materials stocks tracked strong commodity prices, while a retreat in U.S. Treasury yields eased fears of rising U.S. inflation. * At 9:30 a.m. ET (14:30 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 125.06 points, or 0.67%, at 18,815.06. (Reporting by Amal S in Bengaluru; Editing by Devika Syamnath)