Experimental evolution to increase the efficacy of the entomopathogenic fungus Beauveria bassiana against malaria mosquitoes: Effects on mycelial growth and virulence

Abstract

Entomopathogenic fungi such as Beauveria bassiana are currently considered as a potential control agent for malaria mosquitoes. The success of such strategies depends among others on the efficacy of the fungus to kill its hosts. As B. bassiana can use various resources for growth and reproduction, increasing the dependency on mosquitoes as a nutritional source may be instrumental for reaching this goal. Passage of entomopathogenic fungi through an insect host has been shown to increase its virulence. We evaluated the virulence, fungal outgrowth, mycelial growth rate, and sporulation rate of two B. bassiana isolates (Bb1520 and Bb8028) that underwent 10 consecutive selection cycles through malaria mosquitoes (Anopheles coluzzii) using an experimental evolution approach. This cycling resulted in an altered capacity of evolved B. Bassiana lineages to grow on different substrates while maintaining the ability to kill insects. Notably, however, there were no significant changes in virulence or speed of outgrowth when comparing the evolved lineages against their unevolved ancestors. These results suggest that fungal growth and sporulation evolved through successive and exclusive use of an insect host as a nutritional resource. We discuss the results in light of biocontrol and provide suggestions to increase fungal virulence.

Characterization of a new strain ofMetarhizium novozealandicumwith potential to be developed as a biopesticide

“…The isolate AgR-F177 was demonstrated to be pathogenic against DBM but the efficacy only reached 45.7%, suggesting low virulence against this insect when compared with other fungal species such as Beauveria bassiana, Metarhizium rileyi and Isaria sinclairii that can reach between 80% to 100% mortality (Duarte et al 2016 ). However, it is important to note that having demonstrated the pathogenicity of M. novozealandicum AgR-F177 against DBM, its virulence could be improved using strategies such as accelerated evolution with the host (Valero-Jiménez et al 2017 ).…”

Vector-Focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

“…Besides Bti and Bs, microorganisms such as the bacteria Chromobacterium sp. Panama [ 182 , 183 ] and the fungi Beauveria bassiana [ 184 ] and Metarhizium anisopliae [ 185 ], among others, have demonstrated mosquitocidal activities. The present challenge is to convert these promising observations into products that are ready to be incorporated in mosquito control interventions.…”

Vector-focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

“…Besides Bti and Bs, microorganisms such as the bacteria Chromobacterium sp. Panama [163,164] and the fungi Beauveria bassiana [165] and Metarhizium anisopliae [166], among others, have mosquitocidal activities. The present challenge is to convert these promising observations into products that are ready to be incorporated in mosquito control interventions.…”