Diet influences the gut microbiome of Queensland fruit fly larvae: understanding gut microbiota to improve the quality of mass-reared flies for the Sterile Insect Technique

The Sterile Insect Technique (SIT) is a pest management tool that can help control and eliminate horticultural pests, including the Queensland fruit fly, Bactrocera tryoni (Diptera: Tephritidae). For SIT to be effective, the sterilised mass-reared Queensland fruit flies that are released have to be competitive with their wild male counterparts in attracting wild females for mating. Gut microbiota can influence fly quality, fitness and mating preference. The aim of this study was to characterise the gut microbiome of individual Queensland fruit fly larvae from domesticated populations reared on artificial diets and wild populations. This characterisation will determine the potential to improve the quality and mating performance of mass-reared fruit flies via a greater understanding of their gut bacteria. We utilised a novel, near full-length (>1300 bp), 16S rRNA gene amplicon next-generation sequencing method. Clustering of the near full-length sequences at 99% similarity revealed low midgut bacterial diversity (max. 13 OTUs) in the larvae. The diversity was found to be significantly lower in the domesticated colonies. The influence of the diet on the gut microbiome is apparent; bacterial genera commonly found in fruit were detected in wild larvae but mostly absent from domesticated larvae. In addition, larvae feeding on the same diet, whether the same single fruit or artificial diet, shared similar gut bacteria. A single bacterial genus, Asaia, was detected in all but one of the 56 individual larvae analysed, which suggests that it could be important for Queensland fruit fly larvae. Further investigations into Queensland fruit fly gut microbial ecology could lead to improved artificial diets enhancing the quality and performance of mass-reared Queensland fruit flies for SIT approaches.