Evidence of two lineages of the symbiont 'Candidatus Erwinia dacicola' in Italian populations of XXXX (Rossi) based on 16S rRNA gene sequences.

@entity25146 @entity238
The close association between the @entity25146 @entity25146 (Rossi) (Diptera: Tephritidae) and bacteria has been known for more than a century. Recently, the presence of a host-specific, hereditary, unculturable symbiotic bacterium, designated 'Candidatus Erwinia dacicola', has been described inside the cephalic organ of the @entity238 , called the oesophageal bulb. In the present study, the 16S rRNA gene sequence variability of 'Ca. E. dacicola' was examined within and between 26 Italian @entity25146 populations sampled across areas where olive trees occur in the wild and areas where cultivated olive trees have been introduced through history. The bacterial contents of the oesophageal bulbs of 314 olive flies were analysed and a minimum of 781 bp of the 16S rRNA gene was sequenced. The corresponding host @entity238 genotype was assessed by sequencing a 776 bp portion of the mitochondrial genome. Two 'Ca. E. dacicola' haplotypes were found (htA and htB), one being slightly more prevalent than the other (57%). The two haplotypes did not co-exist in the same individuals, as confirmed by cloning. Interestingly, the @entity25146 populations of the two main Italian islands, Sicily and Sardinia, appeared to be represented exclusively by the htB and htA haplotypes, respectively, while peninsular populations showed both bacterial haplotypes in different proportions. No significant correlation emerged between the two symbiont haplotypes and the 16 host @entity238 haplotypes observed, suggesting evidence for a mixed model of vertical and horizontal transmission of the symbiont during the @entity238 life cycle.
