Submitted to: World Journal of Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2003
Publication Date: 3/1/2004
Citation: Hernandez-Torres, I., Iracheta, M., Galan-Wong, L.J., Hernandez, C., Contreras, J., Jackson, M.A., Pereyra-Alferez, B. 2004. A Paecilomyces fumosoroseus mutant overproducing chitinase displays enhanced virulence against bemisia tabaci. World Journal Of Microbiology and Biotechnology. 20:207-210. Interpretive Summary: The fungus Paecilomyces fumosoroseus is an insect pathogen that is being developed as a biological control agent for various soft-bodied insects including the silverleaf whitefly. Mutants of P. fumosoroseus that overproduce chitinase were identified and characterized. Chitinase is an enzyme that breaks-down the principle component of the insect cuticle, chitin. In bioassays against silverleaf whitefly nymphs, conidia of the mutagenized P. fumosoroseus strain with enhanced chitinase synthesis incited a 2-fold increase in mortality compared to the non-mutagenized, parental strain. These results suggest that a selection strategy based on enhanced chitinase activity may be used to identify strains of P. fumosoroseus with improved biocontrol efficacy.
Technical Abstract: A Paecilomyces fumosoroseus strain was mutagenized with ultraviolet radiation in order to obtain chitinase-overproducing mutants. Among 200 colonies, we choose one mutant (M84), which showed a larger and stable chitin hydrolysis-halo. Glucose consumption and biomass production were very similar for M84 and parental strains. The chitinase enzyme was inducible by chitin and repressed by glucose in both strains. When they were grown on a minimal medium plus colloidal chitin as sole carbon source, the parental and M84 strains yielded 198 and 690 umoles of N-acetylglucosamine, respectively. These results indicate that the mutant strain synthesized a chitinase with higher activity. Bioassays against Bemisia tabaci nymph showed that M84 incited a 2.0-fold higher incidence of disease compared to the parental P. fumosoroseus strain.