The nematicidal effects of the bacteria Pseudomonas oryzihabitans and Xenorhabdus nematophilus on the root-knot nematode Meloidogyne javanica

In two laboratory experiments and one pot experiment the influence of the b acterial symbionts Pseudomonas oryzihabitans from Steinernema abbasi and Xe norhabdus nematophilus from S. carpocapsae on the root-knot nematode Meloid ogyne javanica was investigated. Exposure of egg masses of M. javanica to t he bacteria and their metabolites resulted in reduced hatching of second st age juveniles (J2). J2 in contact with the bacteria and their metabolites e xhibited disorientation and convulsive movements, but when they were washed and placed in fresh water, many regained normal movement. At dosages of 10 (6) and 10(7) cells ml(-1) mortality was 100% after 24 h exposure, Xenorhab dus being more toxic than Pseudomonas. In soil X. nematophilus was ineffect ive but P. oryzihabitans prevented invasion of J2 into tomato roots and the re was evidence that the bacterium or its metabolites interfered with nemat ode development in galls. Overall, the results indicate that P. oryzihabita ns may provide a possible control strategy for root-knot nematodes.