DUBAI — Australian Open champion Serena Williams has pulled out of this week's Dubai Tennis Championships, organizers said Saturday. Officials released a brief message on Twitter saying Williams and Canada's Genie Bouchard had withdrawn from the lucrative WTA event. Williams recently won her sixth Australian Open title but the world No. 1 sat out last week's Fed Cup tie for the United States because of a persistent, nagging cough. No reason was given for Bouchard's withdrawl, after she was awarded a wild card in the event. Venus Williams won the title last year and will be defending her crown at Feb. 15-21 tournament. — Reuters