Aryna Sabalenka easily overcame Zheng Qinwen 6-3 6-2 to retain her Australian Open title on Saturday after dominating the tournament. The second seed becomes the first woman since fellow Belarusian Victoria Azarenka in 2013 to successfully defend the Melbourne title having not dropped a set over the fortnight. Zheng, in her maiden grand slam final, was bidding to become the first Chinese player to win a major singles title since Li Na triumphed in Melbourne 10 years ago. Sabalenka raced into a 2-0 lead and then fought back from 0-40 on her own serve to go 3-0 up. She had the chance to wrap up …