RNA virus diversity, prevalence and host effects in Australian tephritid fruit flies

Abstract

Several tephritid fruit fly species are major horticultural pests across the world, including in Australia. The Queensland fruit fly (Bactrocera tryoni) is Australia's most significant horticultural pest. While substantial research efforts have investigated management-relevant aspects of its biology, genetics and physiology, not much is known about its interactions with pathogens, including viruses. About 40 years ago, the Queensland fruit fly virus of B. tryoni became the first RNA virus to be discovered in tephritid fruit flies, and despite the pathology it caused, this virus has not been investigated further. Since then, new molecular diagnostic tools and high throughput transcriptome sequencing analyses have resulted in the discovery and characterisation of a large diversity of insect-specific viruses across many insect taxa. This thesis investigated three fundamental aspects of the interactions of Australian tephritid fruit fly viruses with RNA viruses: (1) the diversity and characterisation of RNA viruses of Australian and other tephritid fruit fly species using transcriptome analyses and molecular diagnostic tools; (2) the distribution and interactions of a subset of these RNA viruses in field populations of B. tryoni; and (3) the host effects of two RNA viruses in a line persistently co-infected by these two RNA viruses. Herein, we refer to a line as an individually cultured host laboratory population that in this thesis may be attributed to a certain infection status. This thesis fills a major research gap previously identified, the diversity of natural enemies and their role in B. tryoni biology and ecology, by specifically investigating RNA virus interactions of Australian tephritid fruit flies. It contributes towards understanding the dynamics of these viruses in field populations and whether they may affect host fitness. It also informs mass-rearing programs of flies required for pest management strategies such as the SIT. Furthermore, it contributes to research fields of insect-specific viruses and their epidemiology.

Date of Award	2021
Original language	English