Looking for wild plant reservoirs and potential insect vectors for ‘Candidatus Phytoplasma solani’ in “bois noir”-affected vineyards in Bekaa valley-Lebanon

“Bois noir” is a frequent grapevine yellows in the vineyards of Bekaa valley in Lebanon and is associated with ‘Candidatus Phytoplasma solani’. Genotyping through sequencing of the tuf gene and the variable gene stamp mainly revealed the presence of ‘Ca. P. solani’ strains of genotype tuf-b1/ST14. The high incidence of the disease in two vineyard plots cultivar Chardonnay and the aggregation of “bois noir” cases suggested the establishment in the vineyard itself of reservoir plants and insect vectors. Survey of wild plant and potential planthopper vectors led to the detection the same genotype of ‘Ca. P. solani’ in the field bindweed Convolvulus arvensis in the two vineyards as well as in several sites in the Bekaa valley and in Hyalesthes obsoletus populations collected on this plant species. These data suggest the local propagation of ‘Ca. P. solani’ through a classical epidemiological cycle involving bindweed reservoir hosts and H. obsoletus planthopper vectors. Surprisingly, a ‘Ca. P. omanense’-related strain was also detected in an old plantation of Syrah as well as in C. arvensis and two cixiid planthopper species.