Piper Alexander M, Farnier Kevin, Linder Tomas, Speight Robert, Cunningham John Paul
Agriculture Victoria Research, AgriBio Centre, 5 Ring Road, Bundoora, VIC, 3083, Australia.
Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
J Chem Ecol. 2017 Sep;43(9):891-901. doi: 10.1007/s10886-017-0877-1. Epub 2017 Aug 23.
Yeast-insect interactions have been well characterized in drosophilid flies, but not in tephritid fruit flies, which include many highly polyphagous pest species that attack ripening fruits. Using the Queensland fruit fly (Bactrocera tryoni) as our model tephritid species, we identified yeast species present in the gut of wild-collected larvae and found two genera, Hanseniaspora and Pichia, were the dominant isolates. In behavioural trials using adult female B. tryoni, a fruit-agar substrate inoculated with Pichia kluyveri resulted in odour emissions that increased the attraction of flies, whereas inoculation with Hanseniaspora uvarum, produced odours that strongly deterred flies, and both yeasts led to decreased oviposition. Larval development trials showed that the fruit-agar substrate inoculated with the 'deterrent odour' yeast species, H. uvarum, resulted in significantly faster larval development and a greater number of adult flies, compared to a substrate inoculated with the 'attractive odour' yeast species, P. kluyveri, and a yeast free control substrate. GC-MS analysis of volatiles emitted by H. uvarum and P. kluyveri inoculated substrates revealed significant quantitative differences in ethyl-, isoamyl-, isobutyl-, and phenethyl- acetates, which may be responsible for the yeast-specific olfactory responses of adult flies. We discuss how our seemingly counterintuitive finding that female B. tryoni flies avoid a beneficial yeast fits well with our understanding of female choice of oviposition sites, and how the contrasting behavioural effects of H. uvarum and P. kluyveri raises interesting questions regarding the role of yeast-specific volatiles as cues to insect vectors. A better understanding of yeast-tephritid interactions could assist in the future management of tephritid fruit fly pests through the formulation of new "attract and kill" lures, and the development of probiotics for mass rearing of insects in sterile insect control programs.
酵母与昆虫的相互作用在果蝇科果蝇中已有充分研究，但在实蝇科果蝇中尚未见报道，实蝇科包含许多攻击成熟果实的多食性害虫种类。我们以昆士兰实蝇（Bactrocera tryoni）作为实蝇科模式物种，鉴定了野生采集幼虫肠道中的酵母种类，发现汉逊酵母属（Hanseniaspora）和毕赤酵母属（Pichia）是主要分离菌株。在使用成年雌性昆士兰实蝇进行的行为试验中，接种克鲁维毕赤酵母（Pichia kluyveri）的水果琼脂基质产生的气味排放增加了果蝇的吸引力，而接种葡萄汁有孢汉逊酵母（Hanseniaspora uvarum）产生的气味则强烈阻止果蝇，且两种酵母都导致产卵减少。幼虫发育试验表明，与接种“吸引气味”酵母种类克鲁维毕赤酵母的基质以及无酵母对照基质相比，接种“驱避气味”酵母种类葡萄汁有孢汉逊酵母的水果琼脂基质使幼虫发育显著加快，成虫数量更多。对接种葡萄汁有孢汉逊酵母和克鲁维毕赤酵母的基质释放的挥发物进行气相色谱 - 质谱分析，发现乙酸乙酯、异戊酯、异丁酯和苯乙酯存在显著的定量差异，这可能是成年果蝇对酵母特异性嗅觉反应的原因。我们讨论了我们看似违反直觉的发现，即雌性昆士兰实蝇避开有益酵母，这与我们对雌性产卵地点选择的理解如何契合，以及葡萄汁有孢汉逊酵母和克鲁维毕赤酵母截然不同的行为效应如何引发了关于酵母特异性挥发物作为昆虫载体线索作用的有趣问题。更好地理解酵母与实蝇的相互作用，未来可通过配制新的“诱杀”诱饵以及开发用于无菌昆虫控制计划中昆虫大规模饲养的益生菌，协助实蝇科果蝇害虫的管理。
