Different strategies to kill the host presented byMetarhizium anisopliaeandBeauveria bassiana

Abstract

Studies conducted over the last decades have shown the potential of entomopathogenic fungi for the biocontrol of some insect pests. Entomopathogenic fungi infect their host through the cuticle, so they do not need to be ingested to be effective. These fungi also secrete secondary metabolites and proteins that are toxic to insect pests. In this context, we analyzed the pathogenicity of Metarhizium anisopliae (Metschn.) strains IBCB 384 and IBCB 425 and Beauveria bassiana (Bals.-Criv.) Vuill. strains E 1764 and E 3158 against Galleria mellonella (Linn.) larvae, during pre-invasion and post-invasion phases. The results showed M. anisopliae, especially strain IBCB 384, was most virulent in the pre-invasion phase against G. mellonella, whereas B. bassiana, especially strain E 1764, was most virulent in the post-invasion phase. During in vivo development and in the production of toxic serum, B. bassiana E 3158 was the most virulent. Different fungal growth (or toxin) strategies were observed for studied strains. Metarhizium anisopliae IBCB 425 prioritizes the growth strategy, whereas strain IBCB 384 and B. bassiana strains E 1764 and E 3158 have a toxic strategy. All strains have pathogenicity against G. mellonella, indicating their possible use for biocontrol.

Toxicity of microbial insecticides toward the non‐target freshwater insect Chironomus xanthus

“…219. 53 Organisms were exposed to pre-established sublethal concentrations of Btk [8,20,50 and 126 μg a.i./L, plus control treatment (ASTM hard water only)] and Bb (0.07, 0.14, 0.28, 0.56 μg a.i./L, plus control treatment) for a period of 28 days. First-instar larvae (2 days old) were introduced into 200 mL glass vials containing a 1.5 cm layer of inorganic sediment (< 1 mm), previously burnt at 500 ∘ C for 5 h, and 150 mL of aerated experimental solutions.…”

“…Infectious conidia actively penetrate the integument to infect susceptible insects, by combining both mechanical pressure and enzymatic activity. Grown hyphae invade the hemocoel and exploit the hemolymph for nutrients, and produce toxins such as beauvericin, bassianolide and bassiacridine, leading to insect death . Subsequently, the fungus begins its saprophytic phase by leaving the host body and producing conidia on the outer surface of the dead insect .…”

“…Grown hyphae invade the hemocoel and exploit the hemolymph for nutrients, and produce toxins such as beauvericin, bassianolide and bassiacridine, leading to insect death. 20 Subsequently, the fungus begins its saprophytic phase by leaving the host body and producing conidia on the outer surface of the dead insect. 21 The PEC value for similar Bb-based insecticides (PEC -surface water) is 247 330 μg a.i./L.…”

Análisis de las investigaciones sobre Metarhizium anisopliae en los últimos 40 años

“…Su modo de acción es por contacto (Alcalá-Gómez et al, 2017), contaminando la microflora de la cutícula del insecto, germinando la espora sobre el insecto plaga y la hifa se introduce al integumento (tejido que forma la pared externa de la cutícula del cuerpo de los insectos) e ingresar al hemocele y después propagarse mediante la hemolinfa por todo el insecto, causando su muerte por las toxinas (por toxemia) que este mismo secreta (Petlamul y Prasertsan, 2012). Presenta una gran diversidad genética y por lo regular se desarrolla en hábitats agrícolas (Bidochka et al, 1998;Rustiguel et al, 2018). Algunas de las plagas que controla son: Mosca blanca (Trialeurodes vaporariorum Westwood), trips (Thrips spp), gallina ciega (Phyllophaga spp.…”

“…B. bassiana y M. anisopliae se combinan debido a las estrategias que cada uno sigue, ambos su modo de acción es de contacto, solo que el primero tiene una estrategia tóxica mediante oosporeinas e invade al hospedero mientras que el segundo tiene una estrategia de crecimiento con la formación de apresorios e invasión del hospedero, esto hace que el efecto para el control biológico de plagas sea mayor (Rustiguel et al, 2018). Aunque en otros estudios se han enfocado en establecer cuál de estos dos hongos tiene mejor efecto fungicida (Barbosa et al, 2018), así como sus combinaciones con algunos insecticidas (Rivero-Borja et al, 2018), con diversos compuestos químicos, como el timol, y métodos de aplicación (Sinia y Guzman-Novoa, 2018), para el control de plagas.…”