Indian Journal of Nematology

Rice root-knot nematode, Meloidogyne graminicola is a serious problem of rice crop. Rhizobacteria are considered the most ideal agents for nematode management because of their antibiosis effects due to the metabolites produced and accumulated to a toxic level during their growth. An in-vitro screening was carried out to investigate the antinemic activity of cell-free culture supernatants of 22 strains belonging to five species of rhizobacteria against M. graminicola egg hatching and juvenile motility. All the bacterial strains produced water soluble compounds that adversely affected the mobility of juveniles and egg-hatch. However, Gluconacetobacter diazotrophicus Co99-70; Pseudomonas spp. RKP-33; Bacillus spp. RKB-91 and RKB-68 significantly delayed and decreased nematode egg-hatch and also irreversibly inactivated mobility of 64–77% of the treated juveniles within 24 h of exposure. This also describes a bioassay based screening system for selecting bacterial strains that produce water soluble nematicidal compounds in in-vitro, which proved to be a better and more rapid method of identifying the promising antagonists.