Integrated Control of Tomato Damping-Off Using Stenotrophomonas rhizophila and CuO Nanoparticles

Damping-off caused by Fusarium spp. limits tomato seedling establishment, while chemical control is constrained by resistance development and environmental risks. As a result, biological alternatives and nanomaterials have attracted increasing interest. This study aimed to quantify the in vitro inhibition and in vivo control of Fusarium spp. associated with tomato damping-off using the marine strains KN1 and KN2 of Stenotrophomonas rhizophila and copper oxide nanoparticles (CuO-NPs). Nine fungal isolates were recovered from symptomatic plants; the most virulent isolate (3DR23HA) caused 60% disease incidence and was identified as Fusarium oxysporum. In dual-culture assays, both bacterial strains inhibited mycelial growth, with percentage inhibition of radial growth (PIRG) values exceeding 65% in several isolates, whereas KN1 showed greater inhibition of conidial germination. CuO-NPs exhibited a concentration-dependent response, reaching near-complete suppression at 0.75–1.0 mg mL−1. In seedlings, the inoculated control showed 100% incidence and a disease severity index (DSI) of 85%, whereas KN1, KN1 + CuO-NPs at 0.75 mg mL−1, and KN2 + CuO-NPs at 0.75 mg mL−1 achieved a DSI of 0 and 100% control efficiency, while also improving growth and biomass. Overall, S. rhizophila, particularly strain KN1, and CuO-NPs at 0.75 mg mL−1 represent a promising strategy for the integrated management of tomato damping-off in nurseries.