Different host plants alter structure, diversity, and function of gut bacterial communities in larval instars of Spodoptera frugiperda

Abstract Insect gut microbes have important roles in host feeding, digestion, immunity, and growth and development. The fall armyworm, Spodoptera frugiperda, is a major migratory agricultural pest worldwide, effects of host plants on its communities of gut bacteria remain to be investigated. Therefore, differences in gut bacterial communities were examined in S. frugiperda 5th and 6th instar larvae fed leaves of different host plants (corn, sorghum, highland barley, citrus). Metagenomic DNA was extracted from larval intestines, and abundance and diversity of gut bacteria were determined using 16S rDNA full-length amplification and sequencing. Highest richness and diversity of gut bacteria were in corn-fed 5th instar larvae; whereas in 6th instar larvae, richness and diversity were higher when larvae were fed other crops. Firmicutes and Proteobacteria were dominant phyla in gut bacterial communities of 5th and 6th instar larvae. According to LEfSe analysis, host plant had important effects on structure of gut bacterial communities in S. frugiperda. In an analysis using PICRUSt2 software, most predicted functional categories were associated with metabolism. Thus, the plant species attacked by S. frugiperda larvae affects their gut bacterial communities, and such changes are likely important in adaptation to a host plant.