Exogenous Silicon and Pseudomonas fluorescens Alleviate Meloidogyne javanica Stress in Tomato Plants

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.