Enhancement of entomopathogenic fungal ability to kill Triatoma infestans.

N. PEDRINI; MP. JUÁREZ; R. CRESPO

Valencia, España

Congreso; IX European Multicolloquium of Parasitology.; 2004

The aim of this study is to contribute to the development of new strategies ecologically acceptable for insect control. We proposed the Triatominae cuticular lipids as a new target; the insect surface is covered by a thin layer of lipids, protecting them against water loss and lethal desiccation. Removal of this layer eases microorganisms and toxic penetration. As a tool for insect biological control, entomopathogenic fungi have the ability to infect their host trough the cuticle. The first evidences that Triatoma infestans hydrocarbons were the preferred fungal substrate and, on the complete catabolism of insect-like hydrocarbon by entomopathogenic fungi were obtained in Beauveria bassiana and Metarhizium anisopliae, a variety of intermediate metabolites were also identified (Napolitano R.,  M.P.Juárez. 1997.Arch. Biochem.Biophysics 344:208-214). The biochemical interaction between fungi virulent to Triatoma infestans, low toxity/low dosis of less toxic chemicals, and the insect cuticle were analysed in order to optimize the contact between insecticide agent and the insect. We will describe a methodology based in enhancing the increase the speed of kill. We also established biochemical markers to evaluate the performance of fungal strains of Beauveria bassiana in laboratory conditions. Fungal growth induction on an incubation medium containing insect-like hydrocarbons as the sole carbon source significantly reduced (>17%) the time to kill T. infestans, as compared to controls grown in complete medium. Based on alkane – growth induction of peroxisome proliferation in B. bassiana and other microorganisms as well, we set up a routine, low cost method to compare cuticulae degradation ability of fungal strains or treatments, based in measuring the activity of catalase, the peroxisomal marker enzyme. Quantitation of fungal fermentation products measured by solid phase microextraction (SPME) coupled to capillary gas chromatography (CGC) is an alternative strategy.