Potencial biotecnológico do uso de filtrados de Trichoderma asperellum com indução de quitinases e proteases no controle de larvas de Tenebrio molitor (Coleoptera: Tenebrionidae).

Abstract

Trichoderma sp. it is widely used for controlling various fungi that cause plant diseases, but few studies report their insecticide action. The Trichoderma asperellum species although present in many tropical soils, is still studied with low frequency. Six isolates of T. asperellum the Brazilian Amazon were selected after toxicology screening and evaluated for insecticidal activity against larvae of the beetle Tenebrio molitor, insects are often used as a reference laboratory for testing with biological agents. In this work we used the entomopathogenic fungus Beauveria bassina as positive control and distilled water as negative control in comparison to isolates of T. asperellum. Analyzed spore suspensions at a concentration of 108 spores/mL, filtered with and without enzyme induction of chitinase and protease after T. asperellum growth and B. bassiana in liquid Minimum Medium (MM), on larvae of 3º instar 7. molitor and enzymatic activity of filtered, and also the filtered were autoclaved at 120 º C temperature to see if there is action of enzymes in the middle. The isolates of 7. asperellum that stand out with chitinase containing filtrates were UFRA T192, TI66 UFRA UFRA and T57, as caused mortality of 100, 77,5 and 77,5%, respectively, differing from the positive control causing B. bassiana 50% mortality, and the negative control with sterile distilled water to 2,5%. All treatments 7. asperellum protease induction caused 100% mortality equal to the positive control with B. bassiana. The highest chitinolytic activities were observed for the T. asperellum UFRA T127, T57 UFRA, UFRA UFRA T166 and T175, with 0,21208, 0,18598, 0,18036 and 0,1704 U / ml, whereas B. bassina had lower activity 0,1536 U / mL. Most proteolytic activity obtained was isolated from 7. asperellum UFRA T175 with 0, 54214 U/mL and B. bassiana 0,10899 U/ml. The 7. molitor reduced weight after application of treatments with enzymes. The filtrates were autoclaved isolates that showed lower mortality rates when compared with non-filtered autoclavable. It is concluded that T. asperellum produce chitinases and proteases, and these enzymes are involved in insecticide similar to what occurs with the entomopathogenic fungi.