Experimental transmission of ‘Candidatus Liberibacter asiaticus’ to sour orange seedlings by Diaphorina citri Kuwayama in Cuba.

"Huanglongbing” (HLB) or citrus greening, associated with three ‘Candidatus Liberibacter’ species, is the most serious disease threating the citrus industry worldwide. Up to date, ‘Ca. L. asiaticus’ is the only species reported in Cuba associated with HLB and its insect vector Diaphorina citri Kuwayama. The ability of D. citri to transmit the bacterium under the Cuban environmental conditions has been assumed for years, but never experimentally proven. In two trials of HLB transmission to healthy citrus plants using D. citri, 33 out from the 45 inoculated plants showed symptoms of the disease 6 months after inoculation, and 20 out from of the 23 insect pools used tested PCR positive for ‘Ca. L. asiaticus’. The sequences of four amplicons from the 16S gene were obtained. They showed 100% identity among them and with a number of sequences of ‘Ca. L. asiaticus’ strains; therefore, one sequence per host species was submitted to GenBank. A comprehensive survey on comparable partial sequences deposited in GenBank allowed detecting nine 16Sr SNP lineages determined by the presence of 15 SNPs in at least two sequences when compared with ‘Ca. L. asiaticus’ strain Las_36 (GenBank accession number MK142763) as reference. The sequences from the transmission trials, together with other 27 sequences, did not show SNPs supporting the presence in Cuba of a bacterial strain with a low genetic variability. This is the first report on experimental transmission of ‘Ca. L. asiaticus’ to citrus by D. citri in Cuba.