Considerazioni filogenetiche e biogeografiche su “Candidatus Erwinia dacicola” e prospettive per l’allevamento di Bactrocera oleae (Rossi).

The presence of a hereditary symbiosis in Bactrocera oleae was described by Petri (1909), which highlighted the presence of an oesophageal bulb that harbours bacteria. Within this organ, bacteria continuously multiply, forming masses that are discharged into the midgut. In 2005 this symbiotic bacterium was genetically characterized and its phylogenetic status was investigated. Attempts at cultivation ex situ of the symbiont were not productive, leading to the choice of unculturable status definition. The coevolved bacterium was described as a novel taxon within the family Enterobacteriaceae as ‘Candidatus Erwinia dacicola”. Recently, an extended study showed the presence of three different haplotypes of Ca. Erwinia dacicola with a geographical distribution that appeared not to be random. Moreover, the extension of the studies to the Tephritidae family, showed the presence of specific bacteria in other species. In the mass-rearing of the olive fly Ca. Erwinia dacicola is particularly important. The first mass-rearing of B. oleae on artificial diet was developed in the 60s but it is reported that the symbiont (considered P. savastanoi) was replaced by acidophilus bacteria. In the B. oleae rearing, the microorganism can be lost in particular for the presence of antimicrobial agents. The several attempts to restore the symbiosis have not been successful up to now. The new knowledge on the symbiosis of the tephritid flies and advances in biotechnology give the possibility to improve B. oleae mass-rearing once the symbiont can be successfully reared in vitro.