Big Day For Lorena

Lorena's bogey-free round had eight birdies, of which four came on the par 5s.

MORELIA, Mexico (AP) -- Lorena Ochoa had another big day at the Corona Championship.

The defending champion and top-ranked golfer on the LPGA Tour shot an 8-under 65 on the Tres Marias course to take a one-stroke lead over South Korea's Na Yeon Choi after the first round on Thursday.

"It was a good day, there is really not much more to add if you look at the score, I'm very happy because I'm in control," Ochoa said. "It's very exciting to be in a position that I like, hopefully we can stay there the next three days because my goal is to win it."

The 27 year-old Mexican had a bogey-free round with eight birdies. Last year, she took the lead on the first day and won the tournament with 25-under for her second win at Morelia, where she also won in 2006.

The Tres Marias course features a par-73 layout carved across dry gullies and into steep hillsides. Her two victories in nine LPGA tournaments played in Mexican have both come here.

"There are places where you feel comfortable, and if we compare Morelia with Bosque Real it is true that I feel better in here," Ochoa said. "In Mexico City things are more complicated, the crowd, the course ... It helps to feel good and that's how I feel in this tournament."

Yani Tseng, number two on the rankings, finished with a 69 after bogeying two of her first five holes. Cristie Kerr had a 72 and fellow American Paula Creamer a 79.