(Reuters) - PGA Tour rookie Cody Gribble blew away the field with a closing seven-under 65 to win the Sanderson Farms Championship by four strokes in Mississippi on Sunday.

Gribble, in his eighth start on tour, bolted clear of a tight leaderboard with a hat-trick of birdies from the 15th hole at the Country Club of Jackson.

The left-handed Texan finished at 20-under 268, with compatriots Chris Kirk (70) and Luke List (70) and Englishman Greg Owen (68) equal second on 16-under.

Gribble, 26, barely earned his card to play on the PGA Tour this season, after finishing 40th on the secondary tour ranking.

"It was pretty rough towards the end of the year ... but here I am," he said in an emotional greenside interview.

"There are no words right now. It’s an unbelievable experience."

The low-key tournament, played on the same dates as the WGC HSBC Champions event in Shanghai, gave the tour's lesser lights a chance to shine in the absence of the big boys.

Canadian Graham DeLaet, in his 150th career start, looked prime to post his first tour win when he picked up three front nine birdies.

But a double bogey at the par-five 11th set him back and he eventually finished seven strokes off the pace, equal eighth.

Kiwi Steven Alker had the shot of the day, a hole-in-one with his very first swing.

Teeing off at the 10th hole, Alker made his ace with a five-iron from 212 yards. He finished equal 35th.

(Reporting by Andrew Both in Cary, North Carolina; Editing by Ian Ransom)