Multifunctional MoS₂/PDA@Cu nano-composites suppress tobacco bacterial wilt via enhanced antimicrobial activity,...

Nanotechnology provides a promising formulation strategy for pesticides, offering an effective approach to protect plants against persistent pathogenic threats that cause significant economic losses. In this study, molybdenum disulfide nanoparticles (MoS₂ NPs) were functionalized with polydopamine (PDA) and loaded with copper to form MoS₂/PDA@Cu nanocomposites (MPC). The effectiveness of MPC in controlling tobacco bacterial wilt (TBW), caused by Ralstonia solanacearum (R. solanacearum) was assessed at 62.5-250 μg/mL. Results showed MPC possessed dual functions: high bactericidal efficiency and plant defense activation. Compared with MoS₂ and Cu NPs, MPC displayed pronounced concentration-dependent antibacterial effects against R. solanacearum, primarily by inhibiting bacterial growth, disrupting cellular morphology, damaging cell membranes, impairing motility, and suppressing both two- and three-dimensional biofilm architectures. Furthermore, irrigation with MPC significantly diminished bacterial colonization in tobacco roots, induced the accumulation of reactive oxygen species (H₂O₂ and O₂^-), and enhanced antioxidant enzyme activities in leaves. qRT-PCR analysis showed MPC enhanced the expression of salicylic acid and ethylene pathway-related genes. Notably, at a concentration of 125 μg/mL, pre-treatment with MPC achieved the highest control efficacy (53.85%) against bacterial wilt at 18 days post-inoculation, representing a 1.17-fold and 1.31-fold improvement over 250 μg/mL MPC and the commercial bactericide Thiodiazole‑copper (TCO), respectively. Additionally, under the tested conditions, MPC treatment not only promoted the accumulation of dry matter in tobacco roots but also exerted no adverse effects on four selected non-target organisms. These findings provide mechanistic insights into the suppression of soil-borne diseases by MPC and underscore its significant potential as a sustainable crop protection strategy.