Metabolism of Resistant and Non-Resistant Solanum nigrum L. in Response to Pendimethalin in Cotton Fields

Solanum nigrum L. is an invasive weed in Xinjiang cotton fields, and an important factor affecting cotton quality and reducing cotton yield. Pendimethalin is the most commonly used pre-emergence herbicide on cotton. However, the status of S. nigrum resistance to pendimethalin and the physiological and biochemical mechanisms remain poorly understood. In this study, we investigated how S. nigrum regulates nutrient accumulation, protective enzyme activity, and metabolic enzyme activity in the body to resist injury following pendimethalin exposure. The results showed that the resistant BL‑1 population developed a higher level of resistance to pendimethalin than the sensitive SHZ‑8 population, with a resistance index of 26.20. After pendimethalin treatment, the activity of cytochrome P450 and glutathione S‑transferase enzymes was significantly higher in the resistant biotype than in the sensitive biotype, with peak values of 0.27 U L⁻¹ and 0.22 U L⁻¹ on day 25, respectively. The malondialdehyde and soluble sugar content, and superoxide dismutase activity of both sensitive and resistant biotypes first increased than decreased, but there were no significant differences in peroxidase activity or soluble protein content. The results show that S. nigrum developed a high level of resistance to pendimethalin in Xinjiang cotton fields, and differences in glutathione S‑transferase and cytochrome P450 enzymes associated with pendimethalin metabolism might be related to resistance.