THE EFFECTS OF EXOTOXIN (THURINGIENSIN) FROM BACILLUS-THURINGIENSIS ON MELOIDOGYNE-INCOGNITA AND CAENORHABDITIS-ELEGANS

A partially purified preparation as well as two formulations of exotoxin from Bacillus thuringiensis (thuringiensin) were evaluated for nematicidal activity. The methods used in our evaluations included direct contact nematicidal assays, hatching tests, infection tests in seed pouches using the cucumber/root-knot nematode (Meloidogyne incognita) system, and greenhouse test using the root-knot nematode. While contact nematicidal activity was not observed against juveniles of M. incognita, 100% mortality occurred when the free-living nematode, Caenorhabditis elegans, was used as the test organism. Nematode infection evaluations in the seed pouch assay showed reduced root galling at relatively high concentrations (>10 mg kg-1). Greenhouse assays indicated significant reduction in the soil population. However, the degree of control in relation to the amount of material applied, as measured by the gall numbers, larvae from soil/roots, and plant growth parameters, was not considered adequate. Data on the plant response in relation to treatment with different formulations of the toxin are presented.