Molecular identification and management of Ralstonia pseudosolanacearum (Phylotype I) causing bacterial wilt of tomato using copper oxide nanoparticles in Himachal Pradesh, India

Ralstonia solanacearum species complex comprises a group of highly destructive strains causing bacterial wilt in a wide range of plants. This study reports, for the first time, the identification of Ralstonia pseudosolanacearum (Phylotype I) as the causative agent of bacterial wilt of tomato in Himachal Pradesh, India, using phylotype-specific multiplex PCR. The pathogen was characterized as rod-shaped with length ranging from 1.4 to 1.8 μm using transmission electron microscopy. Additionally, the antibacterial efficacy of metal CuO nanoparticles against Ralstonia pseudosolanacearum was evaluated both under in vitro and in vivo conditions. Characterization of CuO nanoparticles was performed using transmission electron microscopy and Fourier transform infrared spectroscopy, revealing particle sizes between 20 and 100 nm and confirming the presence of Cu-O bonds. In vitro tests demonstrated antibacterial activity of CuO nanoparticles, with inhibition zones ranging from 1.75 ± 0.90 mm at 50 ppm to 11.17 ± 2.89 mm at 500 ppm. In glasshouse experiments, CuO nanoparticles reduced bacterial wilt incidence to 25% at a concentration of 500 mg⁻¹ soil, with generally consistent results observed in the subsequent season.