Effects of different hosts and ages on the diversity of larval gut bacteria in Tuta absoluta

Gut bacterial composition is closely associated with the food intake and developmental age of herbivorous insects. In this study, we aimed to investigate the diversity of larval gut bacteria in different instar stages of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) feeding on different hosts. Gut bacterial DNA was extracted from the 1st, 2nd, 3rd, and 4th instar larvae of T. absoluta feeding on tomatoes, potatoes, and wolfberries for three generations. Subsequently, diversity and richness of gut bacteria were analyzed via the second-generation Illumina MiSeq high-throughput sequencing. Alpha diversity index analysis revealed the highest diversity and abundance of gut bacteria in the T. absoluta larvae fed wolfberry and potato leaves, respectively. The highest gut bacterial diversity and richness were observed in the 1st-instar larvae feeding on potato and tomato leaves. Tuta absoluta feeding on wolfberry leaves exhibited the lowest gut bacterial diversity in the 1st-instar stage and highest abundance in the 2nd-instar stage. Proteobacteria was the dominant phylum in the gut bacteria of stages 1–4 instar larvae feeding on different host plants. The dominant genus was Enterobacter (60.1%) in the 4th-instar T. absoluta larvae feeding on tomatoes and Wolbachia in those feeding on other plants. PICRUSt2 gene function prediction revealed that the larval gut bacteria of T. absoluta played essential roles in food digestion and nutrient supply. Specifically, Wolbachia may enhance nucleotide metabolism in T. absoluta feeding on potatoes. Overall, this study provides a basis to explore the interactions of T. absoluta with gut bacteria and suggests directions for its adaptive evolution and integrated management.