Influence of Host's Plant Diet on Gut Microbial Communities and Metabolic Potential in Spodoptera frugiperda

The gut microbiota of insects, shaped by extensive coevolution, plays a crucial role in host adaptability and ecological expansion. The fall armyworm (Spodoptera frugiperda J.E. Smith), a highly polyphagous and migratory invasive pest, infests more than 350 plant species worldwide, resulting in substantial crop losses and increased reliance on pesticide applications. In this study, we employed 16S rRNA high-throughput sequencing to investigate diet-induced alternations in the gut microbial communities of larvae fed corn, rice, or an artificial diet. The results showed that diet significantly influenced microbial diversity, with rice-fed larvae exhibiting the highest richness. Firmicutes, Proteobacteria, and Cyanobacteria were the predominant bacterial phyla. Genus-level analysis revealed notable diet-dependent shifts, with Enterobacter and other genera (e.g., Ochrobactrum and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium) only detected in plant-fed groups. Additionally, current findings suggest that gut microbial genera are more prevalent when S. frugiperda larvae feed on rice plants than on corn plants or an artificial diet and are closely linked to their metabolic activities. Dominant microbial genera are expected to support essential metabolic processes and exhibit increased abundance on rice. These results indicate that the gut microbiome of S. frugiperda is diet-driven reorganization, potentially facilitating its polyphagy. This study extends the current understanding by elucidating the specific gut microbial taxa and their putative metabolic associations that are responsive to diet in S. frugiperda, thereby providing a theoretical basis for its polyphagous capability and underscoring microbiota-based strategies for sustainable pest management.