(Reuters) - American Lexi Thompson's putter switch helped her surge up the leaderboard to grab a share of the lead at the halfway mark of the ANA Inspiration in Rancho Mirage, California on Friday.
Thompson carded four birdies in her last seven holes, including three in a row from the 12th, to shoot a four-under-68 and jump to seven-under for the tournament in the first major championship of the year.
The 21-year-old joined overnight leader Ai Miyazato atop the leaderboard at Mission Hills Country Club after the Japanese former world number one mixed five birdies and three bogeys on her way to a round of 70.
Six players sit just one shot off the pace, including New Zealand's world number one Lydia Ko, who shot a 68 to go with her first round 70.
American Lizette Salas (67), Norway’s Suzann Pettersen (67), Koreans Park Sung-hyun (67) and Chun In-gee (69) and South African Lee-Anne Pace (70) also shared third place on a packed leaderboard with 19 players within three shots of the lead.
Thompson, who sat in a similar position in 2014 before going on to win the title, changed putters in the lead up to the tournament after a poor result in last week's Kia Classic.
"I started practising with it Tuesday and putted with it an hour and a half a day to get comfortable with it but honestly 20 minutes into it I knew it was good," Thompson told reporters.
"Coming off last week, just how it went for me and I knew where my confidence was I needed a change. It couldn't get any worse. I tried it here and it felt amazing."
The seven-times LPGA tour winner was particularly impressed with her finish in tough conditions.
"The rough is the highest I have ever seen it but that is what majors call for, tight fairways, thick rough and firm greens," she said.
"That's what you get here. I hit a few wayward shots but I recovered well and that’s what you have to do at majors."
Spain's Azahara Munoz, who held the overnight lead with Miyazato, tumbled down the boards with a 78 to drop to one-over and a share of 48th.
Reporting by Ben Everill in Los Angeles, Editing by Nick Mulvenney