Lydia Ko is in a tie for 10th at the halfway mark of the LPGA's CME Group Tour Championship event in Florida.

Ko backed up her first round 71 with another one-under par effort two leave her two-under for the tournament.

The 17-year-old, who yesterday won the LPGA's Rookie of the Year award, started brightly with a birdie on the par-five first, but immediately undid that good work with a bogey on the second.

That theme continued throughout the round, with bogeys on the ninth and 16th holes undermining birdies on the sixth, 11th and 14th.

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Despite that, Ko remains in touch with the leaders - Spain's Carlota Ciganda and Paraguay's Julieta Granada, who are tied at seven under.

A win at this tournament could thrust Ko to the top of the LPGA Tour's order of merit - known as the Race to the CME Globe standings. That would net her a NZ$1.89m bonus to add to her $1.7m earnings this season.