Biocontrol efficacy of native Metarhizium rileyi (Hypocreales: Clavicipitaceae) isolates against Spodoptera litura (F) (Lepidoptera: Noctuidae) and in silico effect of the secondary metabolites against the virulent proteins of the insect.

This study explores the insecticidal potential of secondary metabolites derived from Metarhizium rileyi against Spodoptera litura through an integrative approach involving genomics, metabolomics, and bioinformatics. Four native isolates of M. rileyi were identified and characterized for their insecticidal efficacy. Among these, the SlMr-DOR isolate exhibited the highest effectiveness, achieving a remarkable 90.0% mortality in laboratory bioassays and 93.3% mortality when tested with its crude extract. Gas chromatography-mass spectrometry (GC-MS) analysis of the SlMr-DOR isolate revealed a diverse profile of bioactive volatile secondary metabolites, including squalene, diethyl phthalate, 4-anilinoquinazoline, vinyl 2-ethylhexanoate, 2-phenyl-3-formyl-pyrrole, chloramphenicol, hentriacontane, phthalic acid derivatives, pentacosane, nonanamide, and eicosanoic acid. Among these metabolites, commercially available squalene and diethyl phthalate were further validated for their insecticidal activity through bioassay studies. Molecular docking analysis demonstrated the strong binding affinity of these metabolites with key S. litura target proteins, including putative chemosensory protein CSP8 and α-amylase, revealing their potential mode of action. The results establish that the secondary metabolites, particularly from the SlMr-DOR isolate, are highly effective against S. litura. This study emphasizes the potential of such metabolites as sustainable and effective alternatives for pest management strategies, contributing to integrated pest control approaches and reducing reliance on synthetic chemical pesticides.