Luke Donald's quest to regain the World Number One spot was boosted

Luke Donald's quest to regain the World Number One spot was boosted by an impressive seven under par second round at the Zurich Classic of New Orleans.

The 34 year old needs to finish in the top seven at Avondale to move back above Rory McIlroy and top the Official World Golf Ranking.

That looked unlikely after Donald fired a one over par 73 on Thursday which left him eight shots adrift of the leaders at the Louisiana venue.

However, he stormed back into contention in the second round, kicking off with a birdie at his opening hole - the tenth - before adding four further birdies and an eagle two at the par four first.

The effort moved Donald to six under par, six shots off the lead, held by Jason Dufner.

Dufner, beaten in a play-off in last year's US PGA Championship, also managed a round of seven under par.

The American capped a bogey-free round with an eagle on the par five 18th to reach 12 under and establish a one shot lead over Russell Knox, John Rollins and Ken Duke.

Knox, a 26 year old who was born in Scotland but now lives in Florida, followed his opening round 69 with a 64 which contained an eagle, seven birdies and a bogey.

A further shot back on ten under were South African Ernie Els, Greg Chalmers, who also fired a 64, and Steve Stricker.

Defending champion Bubba Watson had his second straight 71 to make the cut by a stroke in his first tournament since his Masters Tournament win, with Northern Ireland's Graeme McDowell joining him on two under after a second round 73.

Brian Davis was alongside Donald on six under, while fellow Englishmen Greg Owen and Justin Rose were a further shot back.