Phenotypic and genetic characterization of Paecilomyces lilacinus strains with biocontrol activity against root-knot nematodes

Efficient selection of fungi for biological control of nematodes requires a series of screening assays. Assessment of genetic diversity in the candida te species maximizes the variety of the isolates tested and permits the ass ignment of a particular genotype with high nematophagous potential using a rapid novel assay. Molecular analyses also facilitate separation between is olates, allowing the identification of proprietary strains and trace biocon trol strains in the environment. The resistance of propagules to UV radiati on is an important factor in the survival of a biocontrol agent. We have an alyzed 15 strains of the nematophagous fungus Paecilomyces lilacinus using these principles. Arbitrarily primed DNA and allozyme assays were applied t o place the isolates into genetic clusters, and demonstrated that some gene tically related P. lilacinus strains exhibit widespread geographic distribu tions. When exposed to UV radiation, some weakly nematophagous strains were generally more susceptible than effective isolates. A microtitre tray-base d assay used to screen the pathogenic activity of each isolate to Meloidogy ne javanica egg masses revealed that the nematophagous ability varied betwe en 37%-100%. However, there was no clear relationship between nematophagous ability and genetic clusters. Molecular characterizations revealed suffici ent diversity to allow tracking of strains released into the environment.