Effect of some rhizosphere bacteria on root-knot nematodes

Background Root-knot nematodes are among the world's most damaging endoparasitic sedentary nematodes, especially, Meloidogyne incognita that infects a wide range of plant hosts. The activity of different antagonistic bacteria was studied for the low-cost and eco-friendly management of M. incognita on eggplant. Main body Twenty-five isolates were isolated from rhizosphere soils infected with nematodes. Of these, 6 isolates displayed the highest activity, demonstrating 100% mortality of J2 nematodes under laboratory conditions. Partial sequencing of 16S rRNA gene and phylogenetic analysis was used to identify the selected isolates and they were found to be Paenibacillus amylolyticus, Brevibacillus agri, Gluconobacter frateurii, Beijerinckia mobilis, Achromobacter aloeverae, and Pseudomonas stutzeri. The abilities of the selected isolates to produce hydrogen cyanide, siderophores, chitinase, protease, indole acetic acid, and to dissolve phosphorus were also detected. Conclusion The results of the greenhouse experiment indicated that all the tested bacteria had a greatly significant effectiveness for suppressing root-knot nematode M. incognita. Application of all the rhizosphere bacteria and their combinations reduced the number of galls, number of juveniles, egg-masses, eggs, females, and total final population. All bio-agent treatments succeeded in improving the plant growth parameters and increased the microbial density in eggplant rhizosphere.