Pyrimidine safener enhances pretilachlor tolerance and promotes rice seedling establishment

Pre-emergence herbicide safeners are known to protect crop establishment and improve weed control. However, commercially available safeners remain limited and often suppress seed germination and seedling growth. Herein, two compounds, M15 (4,6-dichloro-2-(4-chlorophenyl)pyrimidine) and M17 (4,6-dichloro-2-(3-fluorophenyl)pyrimidine) were synthesized, which exhibited significantly better safening activity than the commercial herbicide safener fenclorim. Under pretilachlor stress, M15 and M17 increased rice seedling emergence, promoted root growth, and enhanced root activity. Transcriptome analysis revealed significant differential expression of cytochrome P450 and glutathione S‑transferases genes related to herbicide detoxification and stress responses with distinct patterns in shoots and roots. Field trials further confirmed that M17 effectively improved seedling establishment while maintaining high detoxification activity against pretilachlor. These results indicate that these novel pyrimidine safeners have promising applications for enhancing crop safety in direct-seeded rice systems.