Evaluation of Nematicidal Potential of Plant Growth Promoting Rhizobacteria against Meloidogyne incognita

Abstract

Root-knot nematodes have a wide host range, causing damage to many annual and perennial crops. More than 100 species of Meloidogyne are known in which M. incognita (Kofoid and White) Chitwood is one of the most common and important plant parasitic nematode in tropical and subtropical regions of the world including Pakistan. Therefore, the present study was planned to check the effect of PGPRs on juvenile mortality and egg hatching inhibition of M. incognita under lab conditions. Eggs were isolated from egg masses by using NaOCl solution. Rhizobacteria (Bacillus subtilis, Pseudomonas fluorescens, Azotobacter chroococcum, Azospirillum sp., Rhizobium leguminosarum) were multiplied on nutrient broth and kept overnight at 28 ± 2 °C in shaking incubator. Cell free culture filtrates were obtained in falcon tubes by centrifuging PGPRs @ 4000 RPM twice for 30 minutes. Two ml of toxins of each PGPR was poured into each 5cm-dia. petri plate and 100 microliters of egg suspension containing approximately 100 eggs were put in each petri plate. Similar experimental conditions and protocols were used for juveniles’ mortality. In this experiment, instead of eggs, 100 J2s contained in 100 microliters of juvenile suspension were put in each petri plate.  The petri plates were placed in completely randomized design in incubator at 28 ± 2 °C with ten replicates. Petri dishes containing distilled water were kept under control. All the PGPRs caused larval mortality and inhibition in egg hatching with varying degrees. The maximum egg hatching was inhibited by Bacillus subtilis while Rhizobium leguminosarum was found the least effective. The other PGPRs i.e. Pseudomonas fluorescens, Azotobacter chroococcum, and Azospirillum sp. showed intermediate results.