Nineteen rhizospheric bacterial isolates and three biocontrol agents (Serratia marcescens, Pseudomonas fluorescens and Bacillus thuringiensis BT14) were evaluated against root-knot nematodes (Meloidogyne incognita). The obtained data revealed that, five bacterial isolates (B38, B39, B78, B91 and B103) and S. marcescens strain were the most effective bacteria against the J2s of M. incognita whereas, these bacteria achieved the highest mortality percentages by more than 94%. Results also indicated that isolate B38 showed the highest mortality percentage of nematicidal volatile activity by 70.3%, followed by S. marcescens and isolate B103. Moreover, isolate B38 succeeded to record maximum hydrolysis zone values of gelatinase, protease and chitinase (4.27, 5.55 and 4.33 cm, respectively). The most potent isolates for bioagent production were chosen and these isolates were identified as Pseudomonas fluorescens B103 and Bacillus subtilis B38. In addition, poly agar medium recorded the highest values for nematicidal activities by B. subtilis B38, Ps. fluorescens B103 and S. marcescens, while Emerson's agar medium lowest one. Bacterial cells suspension showed more efficient mortality on nematode M. incognita compared with their cultural filtrates. The highest mortality percentages were recorded at dilutions 10-1 by all bacterial strains.
Keywords: biocontrol agents, root-knot nematode, nematicidal activities, Pseudomonas fluorescens, Bacillus subtilis, Serratia marcescens. |
