Characterisation and isolation of gut bacterial communities from Queensland fruit fly (Bactrocera tryoni) across different environments to improve the sterile insect technique

The digestive tracts of pest fruit flies (Tephritidae: Diptera) contain a diverse range of bacteria. Since the 1980’s there has been increasing interest in the role of microbial symbionts in tephritid fruit fly performance, rising sharply in the past decade. The sterile insect technique (SIT) is an environmentally safe insect pest management method that has been implemented against several tephritids and other pest insects of economic significance. The efficacy of SIT relies upon sterile males outcompeting field males to copulate with field females, which then fail to reproduce, resulting in suppression of pest populations. Mass production and sterilisation by irradiation can adversely affect several male fly traits. SIT has also been developed and deployed for the control of Queensland fruit fly, Bactrocera tryoni (Froggatt), Australia’s most significant horticultural pest species. Research has shown that bacteria play an important role in tephritid biology, and some bacterial isolates can improve performance traits, including mating competitiveness. However, little is known about the application of symbiotic bacteria in enhancing tephritid performance in SIT operational programs, and this is particularly the case for B. tryoni. Symbiotic bacteria supplied to mass-reared fruit flies may help overcome some of these issues. However, the effects of tephritid ontogeny, sex, diet and irradiation on their microbiota are not well known. The aim of this PhD was to establish the diversity and abundance of bacterial symbionts in the gut of B. tryoni collected from different laboratory and field environments. Overall my research contributes to the wider research effort on the microbiota of tephritid pest fruit flies. Recent advances in sequencing technology have enabled more insights into the diversity and dynamics gut bacterial communities of insects and the roles they play in insect development. Gut bacteria have been demonstrated to improve the performance of tephritid fruit flies and thus are a promising target in improving the sterile insect technique used in tephritid fruit fly management