Detection of ‘Candidatus Phytoplasma brasiliense’ in a new geographic region and existence of two genetically distinct dnaK genotypes

In September 2007, a peach tree (Prunus persica) displaying yellowing symptoms indicative of phytoplasma infection was sampled in Quba region of Azerbaijan. A phytoplasma was detected in the diseased peach tree by nested PCR amplification of its 16Sr DNA with universal primers for phytoplasmas. Phylogenetic analyses of the amplified 16S rDNA showed that the phytoplasma infecting peach tree corresponded to ‘Candidatus Phytoplasma brasiliense’, a phytoplasma not previously reported in the Euro-Mediterranean area. To set up a detection assay, cloning of a ‘Ca. P. brasiliense’ DNA fragment was undertaken by comparative RAPD. The amplified dnaK-dnaJ genetic locus was used to design a nested PCR assay able to amplify all ‘Ca. P. brasiliense’ strains of the subgroup 16SrXV-A without amplifying the related members of the group 16SrII. The use of this assay also confirmed detection for the first time of ‘Ca. P. brasiliense’ in diseased basil collected in south Lebanon.