Characterisation of the Pathogenicity of <i>Beauveria</i> sp. and <i>Metarhizium</i> sp. Fungi Against the Fall Armyworm, <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae)
Nonthakorn (Beatrice) Apirajkamol | Bishwo Mainali | Phillip Warren Taylor | Thomas Kieran Walsh | Wee Tek Tay
Previously, we assessed the pathogenicity of eleven endemic entomopathogenic fungi (EPF), including six <i>Beauveria</i> isolates, four <i>Metarhizium</i> isolates, and one <i>M. pingshaense</i>, against the agricultural pest <i>Spodoptera frugiperda</i> (fall armyworm, FAW). We found that four <i>Beauveria</i> and one <i>Metarhizium</i> isolates were effective, with <i>Beauveria</i> isolates B-0571 and B-1311 exhibiting high mortality within 24 h post-spore application. This study aimed to identify and characterise the entomopathogenesis mechanisms of these isolates as potential FAW biocontrol agents. All <i>Beauveria</i> isolates were determined as <i>B. bassiana</i>, the <i>Metarhizium</i> isolates as two <i>M. robertsii</i>, one <i>M. majus,</i> and an unknown <i>Metarhizium</i> species. Despite the high mortality from B-0571 and B-1311 isolates, scanning electron microscopy showed no fungal spore germination on dead larvae 24 h after spore application. Four insecticide compound gene clusters, i.e., bassianolide, beauvericin, beauveriolide, and oosporein, were identified and characterised in all <i>B. bassiana</i> isolates. These compounds are hypothesised to contribute to the high early mortality rates in FAWs. Identifying and characterising gene clusters encoding these insecticide compounds in B-0571 and B-1311 will contribute to a better understanding of the entomopathogenicity of these isolates that will be vital to developing these EPF isolates as sustainable alternative FAW biocontrol agents.
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