Non-target-site resistance to ALS-inhibiting herbicides in a Sagittaria trifolia L. population

Sagittaria trifolia L. is one of the most competitive weeds in rice fields in northeastern China. The continuous use of acetolactate synthase (ALS)-inhibitors has led to the evolution of herbicide resistant S. trifolia. A subpopulation BC1, which was derived from the L1 population, was analyzed using DNA sequencing and ALS enzyme activity assays and levels of resistance to five ALS-inhibiting herbicides was determined. DNA sequencing and ALS enzyme assays revealed no amino acid substitutions and no significant differences in enzyme sensitivity between susceptible and resistant populations. Whole-plant dose-response experiments showed that the BC1 population exhibited different levels of resistance (resistance ratios ranging from 2.14 to 51.53) to five ALS herbicides, and the addition of malathion (P450 inhibitor) to bensulfuron-methyl, penoxsulam and bispyribac-sodium strongly reduced the dry weight accumulation of the BC1 population compared with the effects of the three herbicides alone. The results of the present study demonstrated that the BC1 population has evolved non-target-site resistance to ALS-inhibiting herbicides. [Display omitted] •BC1 population displayed cross-resistance to five ALS-inhibitors.•DNA sequencing assays revealed that no amino acid substitutions between S1 and BC1 populations.•In vitro ALS enzyme assays showed that no significant differences in enzyme sensitivity between S1 and BC1 populations.•Malathion could reverse bensulfuron-methyl, penoxsulam and bispyribac-sodium resistance in BC1 population.•Non-target-site resistance mechanism might be involved in BC1 population.