The present study was outlined to investigate the role of some bacterial genera as biocontrol agents against Meloidogyne incognita and Tylenchulus semipenetrans. For this purpose, three bacterial filtrations, Bacillus thuringiensis (Bt), Serratia marcescens (Sm) and Pseudomonas fluorescence (Pf) were evaluated. The results exhibited that, Sm and Bt achieved significant effect for suppressing nematode juveniles with immobilization rate of 100% against the concerned nematode species. On the other hand, the minimum effect was achieved using Pf with 21% against M. incognita.
Egg-hatching test was conducted using 96-well tissue culture plates with the bacterial filtrations against M. incognita and T. semipenetrans eggs. Sm and Pf show significant inhibition rates of egg hatch against tested nematode species. Sm achieved the highest effect against M. incognita with egg hatch of 41.9% after 13 days, while the egg hatch of T. Semipenetrans was not affected with filtration of Bt.
Filtrate mixtures of bacterial genera varied in their effects with respect to the presence of the genus Serratia in the mixture that shows an obvious effect against juveniles and egg hatch of both nematode species.
Thin Layer Chromatography (TLC) was used for separating the active volatile organic compounds (VOCs) of the bacterial filtrates with different organic solvents. Fractions of the bacterial extracted culture broth were assayed for their activities against T. semipenetrans. Bioassay-guided fractionations of the extracted broth were undertaken to identify the compounds using Gas Chromatography-mass spectrometry) GC-MS).