* Pressel fires flawless 67 to top leaderboard
* Miyazato alone in second after a 68
* Ko ties LPGA record for rounds under par (Updates at end of round)
By Mark Lamport-Stokes
RANCHO MIRAGE, California, April 2 (Reuters) - Morgan Pressel reaped the benefits of a recent swing change and flourished in favourable afternoon conditions on Thursday to move one stroke clear in the opening round of the ANA Inspiration, the first women's major of the season.
Former champion Pressel fired a flawless five-under-par 67, while world number one Lydia Ko stayed in touch after equalling an LPGA Tour record for consecutive rounds under par.
On a hot day at Mission Hills Country Club where the early starters had to contend with strong winds, Pressel birdied two of her first three holes and signed off with her fifth of the day at the par-five last.
Pressel ended the round a stroke in front of Japan's Ai Miyazato, with South Korean Ryu So-yeon, Frenchwoman Gwladys Nocera, American Alison Walshe and 54-year-old Hall of Famer Juli Inkster grouped at 69.
"I kept the ball in play most of the day, I was never really in terrible position," said Pressel who, at 18, became the youngest winner of a women's major at the 2007 Kraft Nabisco Championship held here at Mission Hills.
"I just was very steady. There are a lot of tight tee shots out here, and I was able to hit it where I wanted to so I'm just happy with the way I played today.
"This afternoon there was not much wind at all, a little on the front nine, but not nearly what it was in the morning. So we definitely got a little fortunate with the conditions."
The 26-year-old said she had benefited greatly after working hard over the past month on a swing overhaul with one of her former coaches.
"I'm trying to keep better posture and get the club more in front of me essentially," she told reporters. "Honestly I had no idea where the golf ball was going early this year, so it's a big change."
New Zealander Ko, watched by the biggest galleries of the day, battled blustery conditions on her front nine before grinding out a one-under-par 71 that put her in the LPGA Tour record books.
The richly talented 17-year-old, who has yet to win a major but has already claimed six LPGA titles, matched Hall of Famer Annika Sorenstam's run of 29 consecutive rounds under par on the circuit, achieved by the Swede in 2004.
"Overall I'm happy with where I am for this tournament," said Ko, who became the youngest golfer to hold top spot in the world rankings in January.
"It's just pretty cool to tie Annika's record."
Reigning champion Lexi Thompson launched her title defence with a 72 after playing in the more difficult morning conditions, fellow American Michelle Wie carded a 73 and South Korea's world number two Park In-bee returned a 74. (Editing by Peter Rutherford)