Mutagenesis breeding, combined with the application of corresponding herbicides to develop herbicide-resistant rice germplasm, provides great promise for the management of weeds and weedy rice. In this study, a topramezone-resistant rice mutant, TZR1, was developed from the indica rice line Chuangyu 9H (CY9H) through radiation mutagenesis and topramezone selection. Dose-response curves revealed that the resistance index of TZR1 to topramezone was 1.94-fold compared to that of CY9H. The resistance mechanism of TZR1 was not due to target-site resistance. This resistance could be reversed by a specific inhibitor of glutathione