The Impact of Dissolved Biochar on Oxidative Stress and Its Effect on the Virulence of Steinernema feltiae: Implications for Biocontrol Efficiency

Dissolved biochar (DBC) can make a significantly impact on soil ecosystems and the associated biota due to its high environmental bioavailability. However, the impact of DBC on the adaptability of entomopathogenic nematodes (EPNs), such as Steinernema feltiae, remains uncertain. This study investigates the impact of DBC on oxidative stress, antioxidant enzyme activity, virulence, and gene expression in EPNs through culture assays and RNA-seq analysis. Results showed that DBC exposure significantly increased the accumulation of reactive oxygen species (ROS) accumulation. The nematodes treated with DBC700 exhibited 64.34% higher ROS levels, while those treated with DBC400 had 51.13% higher levels compared to the control. Superoxide dismutase (SOD) and catalase (CAT) activities were significantly suppressed, with a stronger inhibition observed in the DBC700 group. As revealed by virulence assays, DBC treatment reduced the infectivity of EPNs against Galleria mellonella larvae. Transcriptome analysis revealed that DBC primarily affected oxidative stress response, membrane transport, and longevity regulation pathways. Moreover, DBC400 predominantly inhibited carbohydrate metabolism, whereas DBC700 significantly impacted oxidative metabolism, protein processing, and neuronal signaling pathways, suggesting the presence of distinct metabolic adaptation mechanisms between the two DBCs. Overall, this study suggests that DBC may impair the biocontrol efficacy of S. feltiae through oxidative stress and genetic perturbations, providing new insights into its long-term ecological impacts on soil ecosystems.