Sept 9 (Reuters) - Canada’s main stock index fell on Thursday, weighed down by weakness in energy stocks, while persisting worries about a slowdown in the economic rebound and rising COVID-19 cases further dented sentiment. * At 9:31 a.m. ET (13:31 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 36.07 points, or 0.17%, at 20,705.72. (Reporting by Amal S in Bengaluru; Editing by Anil D’Silva)