Effects of different hosts and ages on the diversity of larval gut bacteria of Tuta absoluta (Lepidoptera: Gelechiidae)

The composition of the gut bacteria in herbivorous insects is closely related to their food and developmental ages. This study aims to investigate the diversity characteristics of larval gut bacteria of Tuta absoluta (Meyrick) at different instars and feeding on different hosts. The gut bacterial DNA was extracted from the 1st, 2nd, 3rd and 4th instar larvae of Tuta. absoluta feeding on tomato, potato and wolfberry for three generations. Subsequently, the diversity and richness of gut bacteria were analyzed using Illumina MiSeq high-throughput sequencing technology in the 2nd generation. Alpha diversity index analysis showed that there were differences in the structure and diversity of gut bacteria of T. absoluta at different instars and feeding on different hosts. The gut bacterial diversity was highest when feeding on wolfberry (W), and the gut bacterial richness was higher in 1st instar larvae. Proteobacteria was the dominant phylum in the gut bacteria of 1st-4th instar larvae feeding on different host plants. The dominant genus of the 4th instar T. absoluta (T4) feeding on tomato was Enterobacter (60.13%) and the dominant genus of the other samples was Wolbachia. PICRUSt2 gene function prediction revealed that the larval gut bacteria of T. absoluta play an essential role in food digestion and nutrient supply. Wolbachia may enhance the nucleotide metabolism function of T. absoluta feeding on potato. This study demonstrated that different hosts and ages have crucial effects on the structure and diversity of the gut bacterial communities of T. absoluta larvae, which lays a solid foundation for exploring the interactions between gut bacteria and T. absoluta. It provides more perspectives and directions for the adaptive evolution and integrated management of T. absoluta.