US May corn and wheat futures were slightly higher on Tuesday, with both reversing a lower opening. A Chinese rate hike weighed on grains early, but traders said lower corn prices were used as a buying opportunity. Wheat turned higher on concerns about weather conditions in the US Plains. At 9:52 CDT (1452 GMT), May corn was up 2-3/4 at $7.63, while May wheat was up 2-1/2 at $7.92-1/2.