LOS ANGELES (AFP) — Jacob Bridgeman held his nerve as his seven-shot lead dwindled to one, draining a short par putt at the 72nd hole to claim his first PGA Tour title with a one-shot triumph in the Genesis Invitational on Sunday.

The 26-year-old American had started the day with a six-shot advantage that swelled to seven after his birdies at the first and third.

But those were his only birdies of the day, with Bridgeman grinding his way to a one-over-par 72 at iconic Riviera Country Club for an 18-under total of 266 that left him one clear of Rory McIlroy and Kurt Kitayama.

McIlroy started six back in second and carded a four-under 67 while California's Kitayama powered up the leaderboard with a seven-under par 64.

Aussie veteran Adam Scott, winner at Riviera in 2020, had eight birdies in an eight-under 63 to finish alone in fourth on 268.

"I thought it was going to be a lot easier than that," admitted Bridgeman, who had cruised to back-to-back 64s on Friday and Saturday.

His third bogey of the day, from a greenside bunker at the par-three 16th, saw his lead reduced to one.

"I didn't really feel really crazy nervous until I had a five-footer for bogey on 16," Bridgeman said. "That one was sketchy. I hit a really good putt and luckily it went in and then I was really nervous from there on out."

Bridgeman was in a greenside bunker again at the par-five 17th, and two-putted from 21 feet for par.

At hole 18, he put his approach at 20 feet from the pin, and after leaving that one short finally made the winning putt.

"I couldn't even feel my hands on the last couple of greens, just hit the putt hoping it would get somewhere near the hole," he said. "And both of them I left a mile short — I'm glad it's done now."

McIlroy, who completed his career Grand Slam with a Masters triumph last year, had five birdies including a hole-out from a greenside bunker at the 12th.

The Northern Ireland star, who had struggled all week to get to grips with Riviera's challenging greens, said his main reaction was to tell his caddie "it saves us from putting."

McIlroy got up-and-down birdie from a bunker at 17 before he rolled in a 30-foot birdie putt from the fringe at the last.

"Once I started to trust my reads a bit on the back nine and I went more with my first instinct, I putted a little bit better," McIlroy said.

Kitayama, 33, chasing a third tour title, thrust himself into contention with four birdies in his first five holes, and had eight birdies on the day.

McIlroy said he was impressed with playing partner Bridgeman's response to the late challenge.

"He was making a lot of pars and then obviously at the end Kurt did what he did and Adam posted and I started to make a couple birdies," McIlroy said. "It's hard to close out big tournaments. Even though he was a little shaky coming down the stretch, he held it together when he needed to."

World No. 1 Scottie Scheffler, who had to battle to make the cut without a stroke to spare, carded a six-under 65 but still saw his remarkable run of 18 straight top-10 finishes end with his tie for 12th on 11-under.