Mechanisms and improved biocontrol of the root-knot nematodes by Trichoderma spp.

Comprehensive studies in our laboratory revealed the nematicidal potential of waste products from crustacean shells, or other proteinaceous compounds, for controlling species of several plant-parasitic nematodes. The bacteria Telluria chitinolytica sp. nov, and Bacillus cereus, which were isolated, grown and identified in our laboratory, appeared to have potential as bioagents to control the root-knot nematode Meloidogyne javanica. Intensive studies of the mode of action of these bacteria were carried out. The fungus Trichoderma exhibits biocontrol activity against the root-knot nematode M. javanica. Direct fungal parasitism is one of various possible mechanisms by which the fungus can act against the nematode. A constitutive GFP (green fluorescent protein)-transformant of T. asperellum was used to observe the fungal parasitism on nematode eggs and juveniles, using laser scanning confocal microscopy. The involvement of lytic enzymes in the process was demonstrated using inductive GFP-fungal transformants carrying a fusion of the proteinase or chitinase promoters with the gfp gene. These enzyme genes turned on during the interaction between the fungus and the nematodes. The direct fungal parasitism process on the nematode could be improved, in vitro, by using antibodies that bound to the surface of M. javanica J2 and eggs. The presence of these antibodies enhanced the attachment of the spores to the nematodes. This resulted in a significant enhancement of fungal parasitism on the nematodes.