No. 1 seed Ashleigh Barty got off to a rousing start in the Australian Open on Monday, dropping qualifier Lesia Tsurenko of Ukraine 6-0, 6-1 in just 54 minutes.

Barty, an Australian, has never won her home-country major. This is the 15th consecutive time she has advanced to the second round of aGrand Slam tournament and has won two - the French Open in 2019 and Wimbledon in 2021.

Against Tsurenko, Barty fought off two break points and extended her streak to 42 straight games of holding service. She won 73 percent of the points on her first serve, double that of her opponent (36 percent).

"I'm not one for stats at the best of times," she said after the win. "But I think obviously the last five or six matches I felt like I found a really good rhythm on my service games. I've been able to serve my way out of some tricky spots and play some 30-30 points, while not falling too far behind in service games."

In the next round, Barty will meet qualifier Lucia Bronzetti of Italy, who defeated Varvara Gracheva of Russia 3-6, 6-2, 6-3.

Defending champion Naomi Osaka of Japan, the No. 13 seed, also had little trouble moving into the second round, defeating 20-year-old Colombian Camila Osorio 6-3, 6-3 in 68 minutes.

Osaka won 83 percent of the points on her first serve and cashed in on four of six break chances.

"I think I was pretty solid," Osaka said. "I think I was up 5-0 and had a little dip, but I was fortunate enough to close it out. I think that's something that I hope I'm not in that position in my next match. If I am, I already did it this time around, so I guess I'll learn from it."

Next on the schedule for Osaka is American Madison Brengle, who got the win in her opening match when Dayana Yastremska of Ukraine retired in the third set.

The biggest upset of the day came in an all-American match, when Madison Keys knocked out No. 11 Sofia Kenin, the 2020 champion, 7-6 (2), 7-5. Another seeded American, No. 18 Coco Gauff, also made a first-round exit, losing 6-4, 6-2 to Qiang Wang of China.

Keys credited her strong serve for the win. She hit 15 aces to zero for Kenin and won 84 percent of her points on first serve.

"My serve was helping out a lot today, being able to close that out, to start on the front foot and to not have to work my way back into the match was really helpful," Keys said. "I feel I've really found my rhythm with that. It really helped me close out the first and second set in big moments."

Other winners Monday were No. 4 seed Barbora Krejcikova of the Czech Republic, No. 5 Maria Sakkari of Greece, No. 8 Paula Badosa of Spain, No. 15 Elina Svitolina of Ukraine, No. 21 Jessica Pegula, No. 22 Belinda Bencic of Switzerland, No. 24 Victoria Azarenka of Belarus, No. 26 Jelena Ostapenko of Latvia, No. 28 Veronika Kudermetova of Russia, No. 30 Camila Giorgi and No. 32 Sara Sorribes Tormo of Spain.