Multilocus sequence typing reveals the important genetic diversity of ‘Candidatus Phytoplasma solani’ isolates associated with ‘Bois Noir’ grapevine yellows in Azerbaijan. Multilocus sequence typing reveals the important genetic diversity of ‘Candidatus Phytoplasma solani’ isolates associated with ‘Bois Noir’ grapevine yellows in Azerbaijan

Bois noir (BN) caused by ‘Candidatus Phytoplasma solani’ (‘Ca. P. solani’), is an important grapevine yellows disease in viticultural regions of the Euro- Mediterranean basin. The aim of the present work was to evaluate the genetic variability of BN phytoplasma isolates from Azerbaijan. For this purpose BN phytoplasma isolates from Azerbaijan were characterized by multilocus sequences analysis (MLSA), which is the most appropriate method for genotyping of prokaryotes. MLSA of ‘Ca. P. solani’ grapevine isolates were performed by the sequencing of two non-ribosomal house-keeping genes (secY and tuf), stamp gene encoding a membrane protein and a recently characterized citS gene encoding a malate/citrate transporter. The Azerbaijanian BN phytoplasma isolates corresponded to three different tuf genotypes and three distinct secY genotypes, one of them corresponding to the most common genotype found in Europe and the others being two new genotypes. Sequence of stamp gene allowed differentiating four genotypes not previously described. A finer Azerbaijanian BN isolate differentiation was obtained with CitS genotyping as five different genetic variants were evidenced; among which two corresponded to the new genotypes. Altogether these results indicate an important genetic diversity of BN phytoplasmes in Azerbaijan which is inconsistent with introduction by infected material for planting from Western Europe, but could rather result from spread through local insect vectors.