Seasonal variations in the Bactrocera oleae (Rossi) (Diptera: Tephritidae) microbiome

Bactrocera oleae is well-known for the wide symbiotic relationships linked with the adult and larval stages phenology. In the whole microbiome of the fly stands out the primary bacterium "Candidatus Erwinia dacicola", usually vertically transmitted and hosted in an oesophageal diverticulum, the "Bulb," and in the gut of larvae and adults. Quantitatively, the titer is not so much high in the new-emerged adults. Still, it increases quickly during the first days until it is impossible to remove the bacterium through oral antibiotic administrations after the fifth day. Due to the peculiar characteristics of "Ca. Erwinia dacicola" and its symbiotic relation with the fly, it is commonly used as an indicator to evaluate the actual symbiotic titer. The absolute quantization of "Ca. Erwinia dacicola" was obtained with Real-Time qPCRs after an extraction of both symbionts and host DNAs from the heads and the abdomens separately, on pools of 4 females. The wild adults were obtained from olives attacked by B. oleae and collected in Portici (NA) all along the fly's activity period, from June to the end of December, for two subsequent years. The results highlighted a cyclical and seasonal variability in the symbiont presence that follows and adapts to the seasonal modifications acting on the phenology of the host and modifying its physiology due to the environmental and climatic conditions. Such results underline the need to accurately define the timing and control techniques of the fly populations based on the alteration of the fly's microbiome.