Efficacy of Entomopathogenic Nematode (Steinernema pakistanense) in Suppressing Root-Knot Nematode (Meloidogyne incognita) on Tomato

Abstract

The present study assessed the biocontrol potential of Steinernema pakistanense (SG1 and SG2 strains) and cell-free culture filtrates (CFCFs) of their bacteria, Xenorhabdus spp., against Meloidogyne incognita in in vitro and greenhouse experiments, offering an eco-friendly alternative to costly and resistant-inducing nematicides. The application of S. pakistanense significantly influenced plant growth and nematode infestation parameters. Higher application rates improved plant growth, with (Nematicide + 1000 RKN) and (1000 EPN + 1000 RKN) treatments showing the highest shoot length, root length, and shoot weight. Contrariwise, nematode infestation was significantly reduced with increasing S. pakistanense application. The control treatment exhibited the highest infestation levels, while (Nematicide + 1000 RKN) treatment nearly eliminated nematode populations. SG1 strain generally showed slightly better suppression than SG2 strain. Application timing also affected plant growth and nematode reproduction. ‘EPNs applied one week before RKNs’ resulted in the best plant growth and lowest nematode reproduction, while ‘EPNs applied one week after RKNs’ exhibited the weakest plant performance and highest nematode populations. ‘Simultaneous application’ had intermediate effects. These findings suggest that pre-application of S. pakistanense enhances plant growth and nematode suppression. Moreover, Xenorhabdus CFCFs demonstrated strong inhibitory effects on M. incognita egg hatching. Higher concentrations (90% CFCF) showed the greatest suppression, with up to 79.25% inhibition for SG1 and 77.12% for SG2. Lower concentrations resulted in progressively higher egg hatching rates, while the control exhibited no inhibition. These results highlight the potential of S. pakistanense and its bacterial symbionts as effective biocontrol agents against root-knot nematodes.