Abstract
In this study, the biological control effects of the Pseudomonas fluorescens strain CHA0 were compared to those of silicon (Si), used as a chemical control agent, against Meloidogyne javanica, the causative agent of root-knot disease in tomato plants. Indicators such as the number of M. javanica galls, eggs, egg masses, and the enzymatic activities of peroxidase (POX) and phenylalanine ammonia-lyase (PAL) were analysed. Results showed a significant reduction in the numbers of galls, eggs, and egg masses produced by M. javanica on tomato plants treated with P. fluorescens CHA0 (applied as a soil additive) as well as with Si (applied as a root and foliar treatment). The enzymatic activities peaked on the fifth day post-inoculation with M. javanica and then gradually declined. The greatest increase in enzymatic activities was observed in the combined treatment with M. javanica, P. fluorescens CHA0, and Si (the N+B+SiO2 treatment). The use of P. fluorescens CHA0 and Si enhanced the defence-related enzyme activity in tomato plants against M. javanica. However, high concentrations of Si were shown to inhibit the growth of P. fluorescens CHA0.