Grapevine flavescence dorée symptoms © Sandrine Eveillard

Grapevine flavescence dorée

Flavescence dorée: difficult to detect

Flavescence dorée is difficult to detect because the three characteristic symptoms do not always appear every year or on every shoot. INRA researchers contributed to the development of a specific detection test for this disease that is now widespread in southern Europe. At present, compulsory control measures are in effect over more than half of France’s total vineyard area.

By Pascalle Mollier - Julien Chuche - Denis Thiéry - Daciana Papura - Sylvie Malembic - Alain Blanchard - Xavier Foissac, translated by Daniel McKinnon
Updated on 09/06/2016
Published on 03/26/2013

Three characteristic symptoms

Three symptoms must be present at the same time on a shoot to confirm the presence of a grapevine yellows disease: change in leaf colour, failure to lignify, and inflorescence and grape mortality. Leaf discolouration depends on the varietal; leaves in white varietals become yellow, red varietals become reddish.

Symptoms of flavescence dorée on the red cultivar of Cabernet-Sauvignon.The leaves become red.. © INRA, S. Evaillard
Symptoms of flavescence dorée on the red cultivar of Cabernet-Sauvignon.The leaves become red. © INRA, S. Evaillard
Symptoms of flavescence dorée on white varietal Semillon. The leaves become yellow.. © INRA, S. Evaillard
Symptoms of flavescence dorée on white varietal Semillon. The leaves become yellow. © INRA, S. Evaillard

Plants may be asymptomatic

One of the difficulties in detecting the disease is that symptoms do not always appear every year and may only be present on one shoot or on a small number of shoots.

In addition, Vitis vinifera varietals are not equally susceptible to flavescence dorée and may not present symptoms with equal intensity. Often, rootstocks are hybrids of various American Vitis species and do not present any symptoms. They nevertheless are healthy carriers of the disease.

Other vineyard phytoplasma bacteria present the same symptoms and a detection test is therefore necessary before declaring a zone infected with flavescence dorée. At present, there are two official methods to detect and distinguish flavescence dorée phytoplasma from bois noir phytoplasma: nested PCR and real-time PCR.

A hidden danger

Phytoplasma can also be spread when cuttings are taken or grafted. Flavescence dorée can thus be spread through contaminated planting material such as grafted vines, rootstocks and budwood. Flavescence dorée is not present across all shoots from a mother plant rootstock and, consequently, not all cuttings will carry the phytoplasma, making this transmission method all the more insidious.

War is declared

At present, compulsory control measures are in effect over more than half of France’s total vineyard area. Flavescence dorée is also found across other countries in southern Europe such as Italy, Portugal, Serbia and Switzerland. It was declared a quarantine pest by the European Union in 1993. Control of the leafhopper vector in all graft and rootstock nurseries across France has been made compulsory by ministerial decree, as has its control for vines in production in wine-growing areas infected with flavescence dorée.

Distribution – implementation of control measures (in French): The two maps show change in the implementation of treatment measures. They do not directly show the spread of the disease because there is a tendency in areas which had three compulsory treatments in 2005 to reduce the number of treatments when disease is no longer present.

Reference

Pelletier, C., Salar, P., Gillet, J., Cloquemin, G., Very, P., Foissac, X. et Malembic-Maher, S. 2009. Triplex real-time PCR assay for sensitive and simultaneous detection of grapevine phytoplasmas of the 16SrV and 16SrXII-A groups with an endogenous analytical control. Vitis,48(2): 87-95.