Investigating the mechanisms of flucarbazone-sodium resistance in Bromus japonicus Thunb

Bromus japonicus Thunb. is a hazardous weed in wheat fields in China. One B. japonicus population, HB-1, which was collected in Hebei Province, survived field rate flucarbazone-sodium exposure. To investigate the mechanism of flucarbazone-sodium resistance in the HB-1 population, the herbicide target als gene was isolated, and the in vitro ALS activity was tested. HPLC‒MS/MS was applied to detect flucarbazone-sodium absorption and residue level. Furthermore, RNA-seq and qRT‒PCR were applied to detect genes related to flucarbazone-sodium metabolism or flucarbazone-sodium and its metabolite transport. The results indicated that in resistant population there were no mutations in the als gene sequences or differences in the IC50 of ALS compared with the sensitive population. In addition, als gene relative copy number and expression also showed no difference. However, significantly increased herbicide metabolism was found in the HB-1 population. In the end, four cytochrome P450 genes (C71D55b, C71A1, C71D55, T5H), three glutathione S-transferase genes (GSTZ, GSTU6b, GSTFB), and three ABC transporter genes (ABCC3, ABCF1, ABCG11) were selected and identified as potentially playing a role in flucarbazone-sodium resistance.