CANADA STOCKS-TSX hits six-week low on China fears, commodity prices

* TSX down 136.35 points, or 0.89 percent, at 15,129 * Eight of the 10 main index sectors decline * Tekmira jumps after regulators approve Ebola treatment By John Tilak TORONTO, Sept 22 (Reuters) - Canada's main stock index declined to its lowest in six weeks on Monday with worries about an economic slowdown in China and a drop in commodity prices weighing on shares of natural resource producers. A Reuters poll showed growth in the Chinese factory sector likely stalled in Se