A ‘Candidatus Phytoplasma omanense’-related strain detected in yellowing grapevine, stunted bindweed and Cixiidae planthoppers in Lebanon

Abstract

Grapevine yellows (GY) affecting Lebanese vineyards are reported to be associated with ‘Candidatus Phytoplasma solani’, the bois noir (BN) etiological agent. However, during a field survey in June 2014 for BN in Mansoura municipality of West Bekaa, Lebanon, ‘Candidatus Phytoplasma omanense’ was detected in a grapevine sample, cultivar Syrah, exhibiting leaf scorch and discoloration, using a phytoplasma universal nested-PCR and sequencing of the 1.2 kbp 16SrDNA amplicon. The same 1.2 kbp 16SrDNA sequence could be amplified from Hyalesthes obsoletus and Reptalus sp. Cixiidae planthoppers collected on Convolvulus arvensis (bindweed) plants in June 2014 in Aammiq municipality of West Bekaa. Yellowing and stunted bindweed plants collected in 2015 in Kefraya and Aamiq municipalities of West Bekaa were also found infected with the same phytoplasma strain. A 16S rDNA RFLP assay was designed to differentiate this phytoplasma from ‘Ca. P. solani’ and ‘Ca. P. phoenicium’, which are endemic to the Bekaa region. ‘Ca. P. omanense’ is reported for the first time in grapevine and in Cixiidae planthoppers already known to respectively host and vector ‘Ca. P. solani’ strains associated with BN disease in grapevine. This result highlights the need for a precise survey of phytoplasmas associated to grapevine yellows in the Eastern Mediterranean basin, and for investigating the possible role of ‘Ca. P. omanense’ as a new threat to Euro-Mediterranean viticulture.