* Closing 71 good enough for Reed to claim win
* Holds off strong finishes by Palmer, Johnson (Adds quotes, detail)
Jan 19 (Reuters) - American Patrick Reed survived a few anxious moments and poor swings midway through the final round to seal his second PGA Tour victory by two shots at the $5.7 million Humana Challenge on Sunday in La Quinta, California.
A commanding seven strokes ahead overnight, Reed mixed four bogeys with three birdies in a roller-coaster stretch of eight holes from the fifth but held steady after that to close with a one-under-par 71 on the Palmer Private course at PGA West.
"I wasn't pleased with the round today but I got it done," the burly 23-year-old told Golf Channel after completing a wire-to-wire victory with a 28-under total of 260, finishing two ahead of fellow American Ryan Palmer (63).
"The first three days were kind of grind and go, play as low as you can," said Reed, who became the first player on the PGA Tour to post scores no worse than 63 in each of the first three rounds.
"But Sundays are always a little harder, as everyone knows, and also the flags are a little tougher. I just tried to stick to the game plan, tried to post a decent number."
World number six Zach Johnson, who clinched his 11th PGA Tour title at the Hyundai Tournament of Champions in Hawaii earlier this month, sensationally birdied the last five holes for a best-of-the-week 10-under 62.
Johnson's flawless round left him in a tie for third at 25-under with fellow American Justin Leonard (65), and he will now take a four-week break before returning to the PGA Tour for the Feb. 19-23 WGC-Accenture Match Play Championship in Arizona.
Little-known American Brendon Todd applied early pressure on playing partner Reed with four birdies in the first six holes but then lost momentum as he closed with a 69 to share sixth place at 23 under with 2010 champion Bill Haas (67).
Most eyes on Sunday, however, were focused firmly on Reed in his bid to become only the second wire-to-wire winner at the pro-am event, compatriot Rik Massengale having achieved the feat in 1977 when the tournament was played over 90 holes.
His commanding overnight lead at an event known for its low scoring in the California desert was cut to six after James Driscoll birdied the first two holes, before Reed recorded a two-putt birdie at the par-five second to get to 28 under.
Todd then piled on pressure with birdies at the second, third and fourth - the last of them a perfectly judged 14-foot putt - to trim Reed's advantage to five.
Though Todd faltered with a bogey at the par-three fifth where his tee shot ended up in water, Reed also dropped a stroke there after chipping to nine feet and missing the par putt.
Both Todd and Reed birdied the par-five sixth after reaching the green in two before Reed's lead was cut to four when he bogeyed the seventh, after finding rough off the tee.
If Reed felt any pressure, he was a picture of ice-cool calm playing the par-four eighth where he struck a superb approach to four feet and sank the birdie putt, then parred the ninth to reach the turn five ahead of the chasing pack.
However, he bogeyed the 10th after finding a fairway bunker off the tee and soon after was just three strokes in front when Leonard knocked in a four-foot birdie putt at the par-five 11th.
Reed rebounded with a birdie of his own at the 11th after reaching the green in two and two-putting before apparently succumbing to nerves with an ugly bogey at the par-three 12th, where he chunked his second shot from a greenside bunker.
Johnson's sizzling five-birdie finish briefly trimmed Reed's lead to just two but the burly American immediately rebounded with a birdie at the par-three 15th, pumping his right fist in delight after draining an 18-foot putt.
Reed surprisingly missed a birdie attempt from only six feet at the par-three 17th but rock-solid pars on the last three holes earned him his second PGA Tour victory, having claimed his maiden title at last year's Wyndham Championship.
He also became the event's second youngest winner after Jack Nicklaus, who triumphed in 1963 aged 23 years and 13 days. (Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Gene Cherry/Peter Rutherford)