Cytochrome P450 Enzymes Are Associated with the Innate Metabolic Resistance of Echinochloa crus-galli to Florpyrauxifen-Benzyl

This study aims to identify the resistance mechanism and temperature effects on florpyrauxifen-benzyl (FPB) resistance in Echinochloa crus-galli biotypes with no prior FPB exposure. The SAOJER-R biotype was resistant to FPB, with a resistance factor (RF) of 3.80, decreasing to 1.49 when a CYP450 inhibitor was present. Its RF increased from 2.37 at 25/20 °C to 5.22 at 35/30 °C. FPB and florpyrauxifen acid (FPA) levels were lower in the resistant biotype and in rice than in the susceptible biotype. CYP450 inhibition increased the FPA amount recovered, confirming metabolic involvement. Genes from CYP, GST, UGT, ATP-binding cassette, AKR, and PER families were upregulated in the resistant biotype. CYP71Z-like, CYP704C-like, and CYP81A-like genes are putatively involved in metabolizing FPB in SAOJER-R, requiring functional validation. Overall, the results highlight temperature-dependent metabolic resistance and identify new candidate genes involved in FPB resistance.