Sequence Analysis of New Tuf Molecular Types of ' Candidatus Phytoplasma Solani' in Iranian Vineyards

Abstract

Grapevine Bois noir (BN) is caused by 'Candidatus Phytoplasma solani' ('Ca. P. solani') and is one of the most important phytoplasma diseases in the Euro-Mediterranean viticultural areas. The epidemiology of BN can include grapevine as a plant host and is usually transmitted via sap-sucking insects that inhabit herbaceous host plants. Tracking the spread of 'Ca. P. solani' strains is of great help for the identification of plant reservoirs and insect vectors involved in local BN outbreaks. The molecular epidemiology of 'Ca. P. solani' is primarily based on sequence analysis of the tuf housekeeping gene (which encodes elongation factor Tu). In this study, molecular typing of tuf, through restriction fragment length polymorphism and sequencing, was carried out on grapevine samples from Iranian vineyards. According to the molecular characterization, three molecular types-tuf b1, tuf b5 and tuf b6-were found, with tuf b1 being the most prominent. These data provide further knowledge of tuf gene diversity and question the ecological role of such "minor" tuf types in Iranian vineyards, which have been detected only in grapevines.

Keywords: Vitis vinifera; grapevine; phytoplasma; phytoplasma diseases; stolbur; tuf.

Figure 1

Unrooted phylogenetic tree inferred from the ‘Candidatus Phytoplasma solani’ (‘Ca. P. solani’) strain nucleotide sequences of the tuf gene. Minimum evolution analysis was carried out using the maximum parsimony method. Percentages of replicate trees in which the associated taxa clustered together in the bootstrap test (500 replicates) are shown next to the branches.