PhD student Macquarie University Sydney, New South Wales, Australia
Relationships between tephritids and associated bacteria have been a focus of entomological research particularly due to the potential use of bacterial emissions in pest management. Symbiotic interactions between fruit flies and associated gut bacteria have been well-studied in several tephritids, however, the composition of volatile chemicals from gut bacterial emissions and their role as mediators of fruit fly behaviour is still underexplored. Here we hypothesis that the volatile emissions from fruit flies gut microbionts may attract host flies. To this end, we isolated culturable bacterial species, mostly belongs to the family Enterobacteriaceae and Pseudomonadaceae, from the midgut of wild-collected adult Queensland fruit fly (Bactrocera tryoni), one of the most damaging horticultural pests in Australia. In the preliminary screening trap assay, both male and female adult B. tryoni were attracted to the odors emitted by most cultured isolates (1% to 25% of net attractancy). Among 100 tested isolates, four isolates significantly deterred adult male and female B. tryoni (-1.5% to -14%). Interestingly, one isolate attracted males (5%) but deterred females (-1.5%). Gas Chromatography-Mass Spectroscopy (GC-MS) analyses revealed a number of microbial volatile organic chemicals (mVOCs) in the headspace of liquid cultures of isolated bacteria, including ketones, carboxylic acids, alcohols and S-methyl esters. Gas Chromatography-Electroantennography/Electropalpography (GC-EAG/EPG) of eight isolates with highest attractancy in trap assay revealed 18 chemicals that elicit physiological responses to adult Qflies. This is an important step in understanding fruit fly-bacteria chemical relationships and its potential to develop attractants and potentially repellents for fruit fly pest management.