LONDON, Canada (AFP) ― South Korea’s Ryu So-yeon fired a bogey-free opening round of nine-under par 63 Thursday to seize a one-stroke lead over compatriot Choi Na-yeon at the LPGA Canadian Women’s Open.

Ryu, the 2011 U.S. Women’s Open champion, hit all 14 fairways and needed only 25 putts, reaching 16 of 18 greens in regulation and chipping in with a sand save to stand atop the leaderboard.

“I really feel great about that, especially because before I was going to tee off my warming up shots were really bad,” Ryu said. “So I had zero expectation I could play this low, but I played really well so I’m really happy.”

Ninth-ranked Ryu, whose only other LPGA title came at the 2012 Toledo Classic, had 10 top-10 finishes without a victory last year and has nine more this year without lifting a trophy.

After birdies at the par-3 second and par-5 fourth and seventh holes, Ryu sizzled on the back nine, starting with three birdies in a row from the par-5 10th.

Ryu added another birdie at the 14th and closed with back-to-back birdies as well to edge Choi for the top spot and matched a London Hunt and Country Club record.

“I shot 11-under when I was playing the 2012 Australian Masters but I couldn’t win the tournament,” Ryu said. “I hope I can win this time.”

Choi launched her first round with five birdies in a row before a bogey at the sixth after finding a greenside bunker broke the streak.

She responded with birdies at the par-5 seventh and 10th holes, then birdied the par-3 13th and par-5 16th as well.

“I felt really good about my game but I didn’t really realize I had five birdies in a row,” Choi said. “The main thing is I really didn’t care about numbers.

“I just tried to hit the fairway and then the green and when I had a birdie chance really try to focus to make it.”

Sweden’s Anna Nordqvist was third on 65 with China’s Lin Xi Yu, Spain’s Azahara Munoz, American Danielle Kang and world No. 2 Park In-bee of South Korea sharing fourth another stroke adrift.

Park bagged six birdies in a bogey-free round as well.

Two-time defending champion Lydia Ko opened on 70, a solid start but still seven strokes off the pace in a share of 34th place.

The Korean-born New Zealander had been advised by a specialist to have surgery on her left wrist and the 17-year-old world No. 3 could go under the knife as soon as next month.

Ko has battled pain in her wrist through recent tournaments and coach David Leadbetter has been reported as saying a cyst on Ko’s wrist has grown.

Leadbetter said Ko might need a long period of time to recover from the operation, which probably would not come before next month’s final LPGA major tournament of the season, the Evian Championship in France.

Ko birdied the par-5 fourth and seventh holes around a bogey at the sixth, then added a birdie at the par-5 16th as well.