MELBOURNE, Australia (AP) — The Latest on the Australian Open (all times local):

12:40 p.m.

Defending champion Naomi Osaka has won the opening match in Rod Laver Arena, reeling off the last four games after dropping serve for the only time to beat Marie Bouzkova 6-2, 6-4.

Osaka is aiming to be only the ninth woman to successfully defend the Australian Open title. She wasn't able to do that at the U.S. Open last year, when she lost in the fourth round a year after winning her first major title in New York, but says she learned some valuable lessons there. “Definitely, it was really tough for me trying to control my nerves. I’m really glad I was able to finish it in two," Osaka said.

She was given the first match on the main court at Melbourne Park on a day when former champions Serena Williams, Novak Djokovic and Roger Federer will also feature on Rod Laver.

“Thanks everyone. You probably didn’t come for me, but thanks for filling up the stadium,” she said.

Osaka hit 29 winners and 28 unforced errors, pushing No. 59-ranked Bouzkova around with some heavy ground strokes.

Other seeded players advancing included No. 13 Petra Martic and No. 14 Sofia Kenin.

Martic had a 6-3, 6-0 win over Christina McHale and Kenin beat Italian qualifier Martina Trevisan 6-2, 6-4.

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11:55 a.m.

Radu Albot has withdrawn from the Australian Open before his scheduled first-round match against No. 32-seeded Milos Raonic and will be replaced by lucky loser Lorenzo Giustino, an Italian who is ranked 150th. Albot, who finished 2019 ranked 46th, played for Moldova at the season-opening ATP Cup and lost his three singles matches to Daniel Evans, Grigor Dimitrov and David Goffin in the group stage. Organizers did not immediately release details of Albot's injury.

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11 a.m.

Cloudy skies and the threat of rain greeted players and spectators on Day 1 at the Australian Open, the first Grand Slam tournament of the decade.

Defending champion Naomi Osaka was playing the opening match at Rod Laver Arena against Marie Bouzkova. Following that, Serena Williams begins her quest for a record 24th Grand Slam singles title.

Defending champion Novak Djokovic begins his chase for an eighth Australian Open title and third-seeded Roger Federer starts his campaign for a men's-leading 21st Grand Slam singles title, both in later matches at Rod Laver.

Night matches feature No. 1-ranked Ash Barty, who is hoping to become the first Australian woman to win her home major since 1978, and an American veteran playing a rising star — Venus Williams vs. Coco Gauff.

Weather forecasters are saying there's a 100% chance of showers along with the possibility of thunderstorms. A high temperature of 21 Celsius (70 Fahrenheit) is expected.

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