Insecticidal and insect growth regulatory activities of secondary metabolites from entomopathogenic fungi, Lecanicillium attenuatum

Abstract

Insect growth regulators (IGRs) are effective alternatives to chemical insecticides because of their specificity and low environmental toxicity. Entomopathogenic fungi are an important natural pathogen of insects and have been developed as biological control agents. They produce a wide range of secondary metabolites such as antibiotics, pesticides, growth‐promoting or inhibiting compounds and insect attracting agents. In this study, to explore novel IGR substances from entomopathogenic fungi, culture extracts of 189 entomopathogenic fungi isolated from Korean soil samples were investigated for their juvenile hormone (JH)‐based IGR activities. Whereas none of the culture extracts exhibited JH agonist (JHA) activity, 14 extracts showed high levels of JH antagonist (JHAN) activity. Among them, culture extract of JEF‐145 strain, which was identified as Lecanicillium attenuatum, showed the highest insecticidal against Aedes albopictus and Plutella xylostella. At liquid culture condition, JHAN activity was observed in culture soup rather than mycelial cake, indicating that substances with JHAN activity are released from the JEF‐145 strain during culture. Furthermore, while extract from solid cultured JEF‐145 strain showed insecticidal activities against both A. albopictus and P. xylostella, that from liquid cultured fungi showed insecticidal activity only against A. albopictus, indicating that L. attenuatum JEF‐145 strain produces different kinds of secondary metabolites with JHAN activity depending on culture conditions. These results suggested that JHAN substances derived from entomopathogenic fungi could be usefully exploited to develop novel eco‐friendly IGR insecticides.

Discovery of entomopathogenic fungi across geographical regions in southern China on pine sawyer beetle Monochamus alternatus and implication for multi-pathogen vectoring potential of this beetle

“…Referring to the potential distribution preferences of entomopathogenic fungi, certain species or their phylogenetically close species matched well with the high frequencies at which they were isolated and the environmental conditions for their optimal growth. For example, L. attenuatum was isolated from soil in Korea (Woo et al, 2020) and from M. galloprovincialis in Spain, which are located at high latitudes. L. flavidum, its congeneric species, was demonstrated to have a narrow growth temperature range from 18°C to 21°C, with no growth at 27°C (Zare and Gams, 2008).…”

The Chemical Ecology Approach to Reveal Fungal Metabolites for Arthropod Pest Management

“…Screening of more than a hundred extracts from cultures of various types of EPF did not lead to the detection of agonists of juvenile hormones, while approximately 10% of the tested extracts had antagonistic activity against these hormones. An extract of the Lecanicillium attenuatum strain JEF-145 displayed the highest level of antihormonal and insecticidal activity against Aedes albopictus and P. xylostella [ 99 ].…”

Juvenile hormone inhibitory and mosquito larvicidal substances derived from actinomycetes

“…As the mode of action of juvenile hormone and its receptor methoprene-tolerance were revealed, the development of a novel screening system has been made (Charles et al 2011;Jindra et al 2013;Jindra et al 2015;Lee et al 2015). Through the high throughput screening system using yeast two-hybrid, it has become possible to indirectly screen massive amounts of juvenile hormone agonists and antagonists without a direct investigation from plant extracts (Lee et al 2018;Park et al 2020), fungi (Woo et al 2020), and actinomycetes (Kim et al 2020).…”