LAS VEGAS >> Southern California wrapped up its rocky season by rolling over Fresno State in the Las Vegas Bowl.

Cody Kessler passed for 344 yards and a bowl-record four touchdowns in the Trojans’ 45-20 victory over the 21st-ranked Bulldogs on Saturday under Clay Helton, their third head coach in less than three months.

Marqise Lee and Nelson Agholor had two touchdown catches apiece, Javorius Allen rushed two more scores, and the Trojans (10-4) answered every question about their motivation by dancing on the sideline while routing a BCS contender for the storied program’s first postseason victory since 2009.

Derek Carr passed for just 217 yards and two TDs in his final game at Fresno State (11-2), which fell behind 35-6 at halftime and failed to secure the first 12-win season in school history.

From Kessler’s smooth offense to a dynamic defensive effort against Fresno State’s FBS-best passing game, USC was uniformly outstanding in its only game under Helton.

The offensive coordinator filled the one-game gap between coaches Ed Orgeron and Steve Sarkisian on the Trojans’ coaching carousel, but USC picked up right where Orgeron left off after its desultory start to the season under Lane Kiffin.

Kessler even outdid Carr, his fellow Bakersfield native and friend, setting the Las Vegas Bowl record for TD passes before halftime and finishing 22 for 30. USC scored three touchdowns in a nine-minute burst in the second quarter, and Allen clinched it with his second TD run with 4:44 to play.

The Trojans even put on a show off the Strip: The entire USC bench twice bounced onto the field during spontaneous group dances after touchdowns, displaying the excitement and confidence so common during the Trojans’ halcyon years under Pete Carroll.

Carr, the nation’s leader in yards passing and total offense, became the fourth player in NCAA history to surpass 5,000 yards passing and 50 TD passes during the game. But Carr leaves Fresno State without a bowl victory, never getting the Bulldogs moving against one of the nation’s best pass defenses.

Fresno State’s two TD catches by Isaiah Burse and Davante Adams both came on short drives resulting from USC mistakes on special teams, and Derron Smith returned an interception 41 yards for a touchdown in the opening minute of the fourth quarter.

The Mountain West champions still haven’t won a bowl game since 2007, losing six of their last seven.

Lee had seven catches for 118 yards in likely the final game at USC for the Biletnikoff Award-winning receiver. The junior is expected to head to the NFL after putting a pleasant finish on a crazy season in Los Angeles.

Kiffin was fired in late September, and Orgeron revived the program with a 6-2 finish to the regular season before resigning in anger when USC hired Sarkisian for the full-time job. Sarkisian watched the bowl game with athletic director Pat Haden in a box above the sellout crowd at Sam Boyd Stadium.

After the teams traded touchdowns on their opening drives, the Trojans blocked Fresno State’s extra point attempt — and it started a deluge.

Agholor caught TD passes of 40 and 17 yards for the Trojans’ next two scores. Allen made a 24-yard TD run through bad tackling midway through the second quarter, and Lee turned a short pass into a 40-yard TD with 37 seconds left in the half.

Kessler threw for 243 yards and set the Las Vegas Bowl single-game record for TD passes in the first half alone, but USC’s defense perhaps was even more spectacular against the nation’s top passing offense.

Carr went 30 for 54 under constant pressure from the blitzing Trojans, who eliminated Fresno State’s running game and twice stopped the Bulldogs on fourth downs in the first half.