Bio-controlling of root-knot nematode-infected tomato plants using Bacillus licheniformis enriched with nano-selenium

Meloidogyne incognita is one of the most destructive endoparasitic nematodes, causing worldwide significant financial losses in tomato production. The environment and the human health problems arise from the use of chemical nematicides increased the need for the investigation of safe alternatives. Biological control in addition to nanotechnology has attracted the research focus for achieving this approach. In the current study, a local isolate furtherly identified as Bacillus licheniformis was preliminary examined for controlling the survival of M. incognita juveniles in vitro. The results indicated that the examined strain achieved mortality percentage of 68 and 75% for the use of low and high concentrations after 48 h of incubation, respectively. Moreover, the efficiency of the isolated strain in the reduction of sodium selenite solution and the formation of selenium nanoparticles was evaluated. The results indicated the formation of extracellular selenium nanoparticles, estimated by transmission and scanning electron microscopy followed by Energy Dispersive X-Ray (EDX) analysis. Furthermore, by evaluating the impact of the use of selenium nanoparticles-bacterial suspension (Bio-SeNPs) on the mortality of M. incognita juveniles, 86 and 95 % were estimated for low and high concentrations, respectively. Finally, under screen house experiment, the examined Bio-SeNPs significantly reduced the number of juveniles, galls, and egg mass by 90.19, 73.73, and 72.73%, respectively, with a significant improvement in the plant growth parameters.