Evaluation of four rhizobacteria on tomato growth and suppression of root-knot nematode, Meloidogyne javanica under greenhouse conditions, a pilot study

Abstract Growth-promoting rhizobacteria are free-living bacteria that colonize the roots and stimulate the plant growth. Many of these bacteria secrete a range of extracellular metabolites that can be involved in the biological control of plant pathogens. In this study, the effect of four plant growth-promoting rhizobacteria (PGPR) was evaluated on tomato growth parameters as well as biological control of the root-knot nematode (RKN) (Meloidogyne javanica). Tomato seedlings were inoculated with four isolates of PGPR including Pseudomonas fluorescens, Pseudomonas striata, Bacillus subtilis, and Paenibacillus polymyxa and cultivated in the presence or absence of RKN. The results showed that the PGPR significantly increased the plant growth parameters. Bacterial strains also significantly affected the reproductive factor of Meloidogyne javanica significantly so that P. fluorescens and B. subtilis reduced the reproductive factor from 112.15 to 24.94 and 24.96, respectively. Based on these results, among applied rhizobacteria in this study, P. polymyxa can be regarded as the best candidate for promoting the growth and biological control of M. javanica in tomato crop under greenhouse conditions