Artificial Larval Diet Mediates the Microbiome of Queensland Fruit Fly.

Rajib Majumder,Toni A Chapman,Brodie Sutcliffe,Phillip W Taylor,Bernard C Dominiak,Bishwo Mainali,Saleh Mohammad Adnan

doi:10.3389/fmicb.2020.576156

Abstract

Larval diets used for artificial rearing can have a significant effect on insect biology. The Queensland fruit fly (aka “Qfly”), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), is one of the greatest challenges for fruit growers in Australia. The sterile insect technique (SIT) is being developed to manage outbreaks in regions that remain free of Qfly and to reduce populations in regions where this species is endemic. Factory scale rearing is essential for SIT; however, artificial larval diets are known to affect the microbiome of Qfly, which may then affect fly performance. In this study, high-throughput Illumina sequencing was used to assess the Qfly microbiome in colonies reared, for five generations from nature, on two common artificial diets (carrot and gel). At generation five (G5), the microbiome was assessed in larvae, pupae, adult males and adult females and standard fly quality control parameters were assessed together with additional performance measures of mating propensity and survival under nutritional stress. At the genus level, bacterial communities were significantly different between the colonies reared on the two larval diets. However, communities converged at Phyla to family taxonomic levels. Bacterial genera of Morganella, Citrobacter, Providencia, and Burkholderia were highly abundant in all developmental stages of Qfly reared on the gel diet, when compared to the carrot diet. Despite abundance of these genera, a greater percentage of egg hatching, heavier pupal weight and a higher percentage of fliers were found in the Qfly reared on the gel diet. Mating propensity and survival under nutritional stress was similar for adult Qfly that had been reared on the two larval diets. Overall, our findings demonstrate that the artificial larval diet strongly influences the microbiome and quality control measures of Qfly, with likely downstream effects on performance of flies released in SIT programs.

Highlights

Insects brought into the laboratory from nature and reared over multiple generations are confronted by a new environment that is very different from nature, and are exposed to significant selection pressures that lead to laboratory adaptation (“domestication”) (Chambers, 1977; Hoffmann et al, 2001)
This genus was more abundant in the pupal developmental stage compared with the larvae, but it was significantly more abundant in the larvae fed on a gel diet (0.5% vs. 0%, false-discovery rate (FDR) corrected p < 0.0001, Figure 4)
The present study provides a comprehensive analysis of how two common artificial diets affect the microbiome of Queensland fruit fly (Qfly) through the early stages of domestication across all developmental stages, along with key quality control and performance parameters

Summary

INTRODUCTION

Insects brought into the laboratory from nature and reared over multiple generations are confronted by a new environment that is very different from nature, and are exposed to significant selection pressures that lead to laboratory adaptation (“domestication”) (Chambers, 1977; Hoffmann et al, 2001). Gut Microbiome of the Domesticated Qfly Reared on Artificial Diet been reported to have significant influence on genetic diversity and numerous life history traits,including development, stress tolerance and reproductive behavior. There are no studies directly comparing the effect of different artificial larval diets on the gut bacterial community of tephritid fruit flies across the developmental stages of larvae, pupae and adult. Previous studies have assessed the bacterial populations of Qfly larvae and Qfly adults reared on a carrot diet and lucerne chaff diet (Morrow et al, 2015; Deutscher et al, 2018; Woruba et al, 2019). This study greatly improves our understanding of how artificial diets affect the microbiome of laboratory reared flies, and has significant implications for factory-scale rearing in SIT programs

MATERIALS AND METHODS

RESULTS

DISCUSSION

Findings

DATA AVAILABILITY STATEMENT