UPDATE 1-Golf-Ochoa takes over number one spot from Sorenstam

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By Mark Lamport-Stokes

LOS ANGELES, April 23 (Reuters) - Mexico's Lorena Ochoa replaced Annika Sorenstam as world number one on Monday, the first time the Swede has been dethroned since the official rankings were introduced early last year.

Although no LPGA Tour event was played last week, Ochoa takes over at the top with a points average of 12.84 from 50 events.

Sorenstam, who is expected to be sidelined until the end of next month because of a ruptured disc in her back, drops to second on 12.70.

"Today is one of the most special days in my life," Ochoa said in a statement released by her management company. "This is a huge accomplishment for me.

"I am extremely happy about becoming the number one player in the world, something that I have dreamed about since I was little.

"And especially this week when I am at home and I am able to celebrate the news with the people in my country," added the 25-year-old, who defends her title in this week's Corona Championship in Morelia, Mexico.

The Rolex rankings, launched in February 2006 by the five major women's professional tours, are adjusted on a rolling two-year calendar with each player's points total divided by the number of tournaments played.