Grain markets traded mostly weaker today, with May Corn futures settling at 449'0 and May Soybean futures falling 8 1/2 cents to 1158'2. However, Wheat futures bucked the trend, as the main Chicago contract added 2 3/4 cents to settle at 598'6. Traders are closely monitoring the fluid geopolitical situation between the U.S. and Iran, while preparing for Thursday's upcoming WASDE release. Ahead of the report, U.S. ending stocks are estimated at 2.128 billion bushels for corn and 349 million bushels for soybeans. South American production is also in focus, alongside the year's first U.S. crop progress report showing corn planting at 3% complete.