MELBOURNE, Jan 20 - Madison Keys began her Australian Open title defence with a nervy 7-6(6) 6-1 victory over Ukraine's Oleksandra Oliynykova on Tuesday, while fellow American Ben Shelton defeated Ugo Humbert in a battle of lefthanders to reach the second round.

Long queues formed outside Melbourne Park for a third straight morning with many keen to watch Jannik Sinner, who faces Hugo Gaston in his first hurdle towards winning a third straight title at the year's opening Grand Slam.