Zach Johnson, Camilo Villegas share lead at John Deere Classic

Defending champion Zach Johnson and Camilo Villegas have finished atop the leaderboard after the first round of the John Deere Classic.

The American shot a bogey-free round of 64 at Deere Run, while the only blemish on the Colombian's card came at the par-four ninth.

Brendon de Jonge, Matt Bettencourt and Daniel Summerhays are one shot further back on six-under-par.

Seven players are on five-under, while KJ Choi and Steve Stricker are among 13 challengers on four-under.

Johnson ended Stricker's three-year stranglehold on the title with victory in last year's event.