Jan 13 (Reuters) - Canada’s main stock index were little changed at open on Wednesday, mirroring subdued moves across global markets, as optimism from gains in energy and materials stocks were capped by concerns around rising global COVID-19 cases. * At 9:31 a.m. ET (1431 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 15.42 points, or 0.09%, at 18,001.22.