Defending women’s champion Serena Williams reached the second round of the Australian Open with a tense 6-4 7-5 win over Italian Camila Giorgi in her first tour match in four months. The American, 34, had been struggling with a left knee injury in the build-up, but came through unscathed. Men’s champion Novak Djokovic eased through in straight sets, beating South Korea’s Hyeon Chung 6-3 6-2 6-4. Roger Federer and Maria Sharapova are also in action in Melbourne on Monday. Djokovic is bidding to equal Australian Roy Emerson’s record of six Australian Open crowns.