Differential Tolerance of Corn (Zea mays) Inbreds to Four Sulfonylurea Herbicides and Bentazon

Nine corn inbreds were selected from a test on 250 inbreds based on distinctly different response to herbicides. These inbreds showed up to 50,000-fold differences, which varied by inbred and herbicide. Only the inbred GA209 was sensitive to bentazon and the four sulfonylurea herbicides. GA209 and B90 were the most sensitive inbreds to the sulfonylurea herbicides. F2R was generally the most tolerant inbred. The pattern of herbicide tolerance varied greatly. For example, the relative tolerance of F2 to thifensulfuron was 12-fold more than to rimsulfuron while Mo17 was 56-fold more tolerant to rimsulfuron than thifensulfuron. F2 was fivefold more tolerant of chlorsulfuron than chlorimuron, whereas B80 was 100-fold the reverse. These inbreds provide a small subset of varieties to evaluate the large and inherent differences in herbicide tolerance of corn.