Lydia Ko has some work ahead to defend her Evian Championship golf major.

The world number one has shot a one-under par 70 in the first round, leaving her in a tie for 27th. Ko had two birdies with her only blemish on the round coming at the eighth hole.

She sits seven strokes behind South Korean joint leaders In Gee Chun and Sung Hyun Park.

Starting in muggy afternoon conditions, Ko played in a group with South Korean Hyo Joo Kim, the 2014 champion, and Norway's Suzann Pettersen, the 2013 winner.


When Ko sank her first birdie of the day, a 15-metre effort on the fifth hole, it drew a rueful smile from Pettersen, who had just missed with her birdie attempt from a similar distance.

Ko bogeyed the eighth hole and she was again in trouble on the 10th when her tee shot landed in the rough between two trees.

She saved par with a good escape shot close to the green.

"It's a good thing my wood shots and chip shots were good enough," said Ko, who last year became the youngest man or woman to be ranked No. 1.

Women's PGA champion Brooke Henderson of Canada ended the day one shot ahead of Ko at 2-under.

World number two Ariya Jutanugarn is further back after firing a two-over 73 which included a triple-bogey seven on the 18th hole.