Monocot diet sources drive diversity of gut bacterial communities in Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae

Microbiome research is currently gaining tremendous interest on the impact of diets and environment to influence life traits of several hosts. Full understanding of the insect ecology and characterization of gut microbial community including their natural enemies is vital for development of novel insect pest management strategies. This study examined the gut bacterial communities of Fall armyworm (FAW) Spodoptera frugiperda reared in the laboratory with three monocot plant diets (Sugarcane [M1], maize [M2] and onion [M3]) using 16S rRNA gene sequencing. The study revealed variations in the structure and community of the gut bacterial biota of FAW larvae reared with three monocot plants. Diet sources greatly altered the structure of the gut bacterial community. Three alpha diversity indices (observed species richness Chao1 and ACE) showed significant differences among the various diet groups. The principal component analysis revealed a moderate distinction in bacterial communities of the FAW larvae reared with the three monocot plants. Higher numbers of operational taxonomic units (OTUs) were observed in sugarcane diet (M1). The bacterial communities of all the larvae groups were dominated by phylum Firmicutes. A redundancy analysis (RDA) indicated that neutral detergent fibre (NDF) (p < 0.0005) was the most significant factors influencing the community distribution of gut bacteria of FAW larvae. Functional Annotation of Prokaryotic Taxa (FAPROTAX) analysis predicted that chemoheterotrophy, fermentation, aerobic chemoheterotrophy and aromatic compound degradation were the prominent putative functions of FAW larvae gut bacteria communities. Chemoheterotrophy was the most dominant putative functions predicted and was higher in sugarcane diet. Furthermore, the complexity of the network structure was higher in M1 while the modularity was higher in maize diet. The different monocot diets had a considerable impact on bacterial composition in the gut of Fall armyworm larvae and their ecological and functional relevance are discussed.