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Characterization of Bois Noir Isolates by Restriction Fragment Length Polymorphism of a Stolbur-Specific Putative Membrane Protein Gene

First and seventh authors: Istituto di Virologia Vegetale, CNR, Strada delle Cacce, 73, I-10135 Torino, Italy; second author: Di.Va.P.R.A.—Entomologia e Zoologia Applicate all'Ambiente “C. Vidano”, Università degli Studi di Torino, via L. da Vinci, 44, 10095, Grugliasco (TO), Italy; third author: Istituto Sperimentale per la Zoologia Agraria, CRA, via Lanciola, 12/A, 50125 Firenze, Italy; fourth author: UMR-1090 Génomique Diversité Pouvoir Pathogène, INRA, Université de Bordeaux 2, 71 avenue Edouard Bourlaux BP81, F-33883 Villenave d'Ornon, France; fifth author: Istituto Sperimentale per la Patologia Vegetale, CRA, via C.G. Bertero, 22, I-00156 Roma, Italy; and sixth author: Dipartimento di Scienze e Tecnologie Fitosanitarie, Università degli Studi di Catania, Via S. Sofia, 100, I-95123 Catania, Italy.

Bois noir phytoplasma (BNp), widespread in wine-producing areas of Europe and endemic in France and Italy, is classified in the 16SrXII-A subgroup, whose members are referred to as Stolbur phytoplasmas. The 16S rDNA gene of Stolbur phytoplasma shows low variability, and few non-ribosomal genes are available as markers to assess variation among isolates. We used the Stolbur-specific stol-1H10 gene, encoding a putative membrane-exposed protein, to investigate genetic diversity of French and Italian BNp isolates from plants and insects. Amplification of stol-1H10 from infected grapevines, weeds, and Hyalesthes obsoletus produced fragments of three sizes, and restriction fragment length polymorphism analysis divided these amplicons further into 12 profiles (V1 to V12). French BNp isolates were more variable than Italian ones, and different profiles were present in infected grapevines from France and Italy. Isolate V3, most abundant among Italian affected grapes but present among French ones, was found in one Urtica dioica sample and in all H. obsoletus collected on this species. Four Italian-specific profiles were represented among infected Convolvulus arvensis, the most frequent of which (V12) was also detected in H. obsoletus collected on this species. Most of the variability in the stol-1H10 sequence was associated with type II on the tuf gene.