Bacteria from the gut microbiome enhance the adaptation of Euschistus heros and Piezodorus guildinii in soybean-producing regions in the Americas

Background: Euschistus heros and Piezodorus guildinii are major soybean pests across the Americas. Gut-associated bacteria can influence insect nutrition, detoxification, and stress tolerance, potentially enhancing adaptation to new hosts and management regimes. We investigated how host genetics and environment shape gut microbiome structure and functional potential in these species. Results: We sequenced the 16S rRNA V4 region from 189 insects collected across Brazil and the United States. Microbiomes were dominated by Proteobacteria and Firmicutes, with high intra- and interpopulation variability. Diversity and community structure varied among lineages and locations: environment explained a larger share of overall variance, whereas host genetics produced clearer group differentiation. In E. heros , genera linked to nutrient acquisition and detoxification (e.g., Pantoea, Wolbachia) were more prevalent; in P. guildinii , Candidatus Benitsuchiphilus associated with diapause and uric-acid metabolism—predominated. Predicted functions included chemoheterotrophy, nitrogen fixation, fermentation, and degradation of aromatic and aliphatic compounds, with distinct patterns across species, lineages, and countries. Conclusions: Both genetic and environmental factors shape the composition and functional capacity of stink bug gut microbiomes, likely enhancing adaptation to diverse hosts and management conditions. These insights open avenues for microbiome-informed strategies to improve the sustainability and efficacy of soybean pest management.