2003Session3.Pdf
THE SITUATION OF GRAPEVINE YELLOWS AND CURRENT RESEARCH DIRECTIONS: DISTRIBUTION, DIVERSITY, VECTORS, DIFFUSION AND CONTROL E. Boudon-Padieu Biologie et écologie des phytoplasmes, UMR 1088 Plante Microbe Environnement, INRA – Université de Bourgogne, Domaine d’Epoisses, BP 86510 – 21065 Dijon Cedex France Grapevine yellows (GY) are known now for 50 years. After the first appearance of Flavescence dorée (FD) in West-South France in the 1950’s, similar diseases have been observed in vineyards of other regions or countries (22) in Europe, North-America, Asia Minor and Australia. Typical symptoms are leaf rolling and discoloration of veins and laminae, uneven or total lack of lignification of canes, flower abortion or berry withering. Eventually, severe decline and death occur with sensitive varieties or with particular GY diseases. All these diseases have been associated with phytoplasmas. Phytoplasmas, discovered in 1967, are wall-less intracellular bacterias restricted to phloem sieve tubes and transmitted only by vector insects in which they multiply and circulate. Recently, comparisons of conserved regions in their genomic DNA, have permitted to classify all known phytoplasmas into about 20 groups and subgroups within a monophyletic clade in the Class Mollicutes, closest to the Acholeplasma clade (57, 78). Numerous DNA probes have been designed that permit diagnosis and identification of phytoplasmas in plant tissues and in insects. This, together with transmission assays, has also permitted the recent identification of new phytoplasma vectors. Though Koch’s postulate cannot be fully satisfied with non-culturable pathogen agents, it is now considered that phytoplasmas are responsible for typical GY symptoms. These conclusions have been reached because of transmission experiments with natural vectors in the case of Flavescence dorée (FD) and Bois noir (BN), of the similarity of symptoms caused world wide by GY diseases on numerous grapevine cultivars and of consistent detection of phytoplasmas in affected grapevines and in infective insect vectors.
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