Busch was involved in an early-race crash with Clint Bowyer, recovered, moved up to the third spot with fewer than 40 laps to go, then experienced motor problems and finished ninth. A seventh-place finish or better would have given him the title despite Edwards' victory.
Edwards led the most laps (109) and easily beat runner-up Kevin Harvick by 2.415 seconds to cut Busch's lead to 190 points.
"I know Kyle has almost clinched the championship, but we came here to win the race," Edwards said after his fifth Nationwide victory and 25th of his career.
Reed Sorenson, Bowyer and Brad Keselowski completed the top five finishers.
Denny Hamlin finished 12th.
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