Zach Johnson retains share of the lead in Illinois

Zach Johnson has carded another flawless round at the John Deere Classic to retain a share of the lead at the half-way stage.

The American, who is defending his title in Illinois, added a 66 to yesterday's effort of 64 to get to 12-under-par.

He is joined at the top by 2009 US Open champion Lucas Glover and Patrick Reed after they shot incredible rounds of 62 and 63 respectively.

Australia's Matt Jones (-11) is one shot further back following his bogey-free second round of 65.

Troy Matteson, David Hearn, Daniel Summerhays, Kevin Streelman and Jerry Kelly all lurk on 10-under-par.

Meanwhile, the best round of the day belonged to Chez Reavie (-9), who signed for a 61.