San Francisco: Canadian teenager Brooke Henderson shot a tournament-record seven-under 65 to grab a two-shot lead after the second round of the LPGA Tour’s Swinging Skirts tournament on Friday.

The 17-year-old Henderson finished 36 holes at nine-under 135 at the Lake Merced Golf Course.

“It’s pretty cool,” Henderson said about setting the record. “This golf course is tough, and the conditions are even tougher.

“On my back nine, the greens really started to firm up and got a little bit faster. You really have to be careful where you place it on the greens.”

Henderson broke Stacy Lewis’ (2014) record of 138 by three shots. The Canadian is looking for her first victory on the US LPGA Tour.

Asked if she was ready to win her first big tournament, Henderson said, “I think I’m ready.

“Yeah, 17 is young. As you’ve seen with Lydia Ko and Lexi Thompson and even Jessica Korda, there are a lot of great names that have been able to do it. I’m hoping that I’m one of them.”

First round leader and defending champ Ko celebrated her 18th birthday on Friday with a even-par 72 to finish tied for fifth.

Choi Na-yeon used a four-under 68 to seize sole possession of second place. Choi finished two rounds at seven-under 137. Japan’s Sakura Yokomine (67) and China’s Feng Yueer (68) are one shot further back and tied for third at six-under.

World number one Ko is tied for fifth with Kwak Min-seo (67), Julieta Granada (69) and Jang Ha-na(71).