Looking at recent market action, one might argue that bulls have the soybean market and bears own the corn market. Maybe this is an obvious conclusion beause once the corn market gets by a summer supply squeeze, U.S. corn supplies appear headed for a record-high level. And on the contrary, U.S. soybean supplies will tighten significantly as the drought-reduced South American soybean production leaves U.S. soybeans to fill world demand at least until March 2013.Lost in the push/pull between corn bears and soybean bulls is the changing role being played by wheat. Simply put, it appears that wheat is quietly replacing corn as the market leader among grains. Evidence of this is the price action of wheat and corn futures during May. From 1 May...