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Lydia Ko is golf's youngest world number one

ANA Inspiration first round leaderboard -5 M Pressel (US); -4 A Miyazato (Jpn); -3 S Ryu (Kor), J Inkster (US), A Walshe (US), G Nocera (Fra); -2 A Ernst (US), N Choi (Kor), C Hull (Eng) Selected others: -1 C Matthew (Sco), L Ko (NZ); +2 J Ewart Shadoff (Eng), L Davies (Eng)

World number one Lydia Ko equalled the LPGA Tour record with her 29th consecutive under-par round in the ANA Inspiration in California.

The 17-year-old carded a one-under-par 71 in the opening round of the first women's major of the season to equal Swede Annika Sorenstam's record.

American Morgan Pressel hit five under par to take the first-round lead.

England's Charley Hull is three shots behind and Scotland's Catriona Matthew a further shot behind with Ko.

New Zealand's Ko, who has won six LPGA Tour titles and is bidding to become the youngest major champion in LPGA Tour history, described her landmark as "pretty cool".

The youngest-ever number one added: "I really wasn't hitting my driver well, and here the rough can get pretty thick.

"When you're in that position, a record was the last thing I was thinking about."

Pressel holds the record as the youngest winner of a major, at 18 years, 313 days when she won this tournament in 2007, as the Kraft Nabisco Championship.

The now 26-year-old birdied two of her first three holes and picked up three more shots on the back nine in a bogey-free round to lead by one from Japan's Ai Miyazato.

American veteran Juli Inskster, 54, who will captain the United States Solheim Cup team in September, is also among the early frontrunners with a three-under-par 69.