Contrasting Susceptibilities to Flavescence Dorée in Vitis vinifera, Rootstocks and Wild Vitis Species.

Sandrine Eveillard,Camille Jollard,Louis Bordenave,Sylvie Malembic-Maher,Pascal Salar,Xavier Foissac,Dima Khalil,Fabien Labroussaa,Jean E Masson,Delphine Desqué,Mireille Perrin,Cyril Hévin,Frédérique Razan

doi:10.3389/fpls.2016.01762

Abstract

Flavescence dorée (FD) is a quarantine disease of grapevine, involving interactions between the plants, leafhopper vectors, and FD phytoplasma. Characterizing the susceptibility of vine varieties could limit disease propagation. After extensive surveys in vineyards, we showed that Cabernet Sauvignon (CS) is highly susceptible, with a high proportion of symptomatic branches and phytoplasma titers, in contrast to Merlot (M). Localized insect transmissions and grafting showed that phytoplasma circulate in the whole plant in the CS cultivar, but in M they are restricted to the transmission point. Insect-mediated transmission under high confinement mimicking natural conditions confirmed these phenotypes and allowed the classification of 28 Vitis accessions into three distinct categories, according to the percentage of infected plants and their phytoplasma titers. Reduced symptoms, low phytoplasma titers, and low percentages of infected plants were found to be associated in the Vitis vinifera cultivars tested. Interestingly, the low susceptibility of M was observed for one of its parents, i.e., Magdeleine Noire des Charentes. Rootstocks and their Vitis parents, although having high percentages of infected plants and intermediate to high phytoplasma titers, shared a symptomless response. This is troubling, because rootstocks can constitute a silent reservoir of contamination in mother plants or when they grow wild nearby vineyards. Altogether, data suggest distribution of genetic traits within the Vitis genus involved in insect-mediated phytoplasma transmission, multiplication, circulation, and symptom development.

Highlights

Phytoplasmas are non-cultivated wall-less bacteria belonging to the class Mollicutes (Weisburg et al, 1989) and are responsible for hundreds of diseases in ornamentals, cultivated plants, and weeds, worldwide
In the three vine plots studied, we showed that the percentage of infected plants and the percentage of symptomatic branches on each stock were lower for M than for Cabernet Sauvignon (CS)
We showed that FDp titers increased along the summer in symptomatic shoots of both cultivars

Summary

Introduction

Phytoplasmas are non-cultivated wall-less bacteria belonging to the class Mollicutes (Weisburg et al, 1989) and are responsible for hundreds of diseases in ornamentals, cultivated plants, and weeds, worldwide. Contrasting Susceptibilities to Flavescence Dorée in Vitis and destructive epidemic diseases of grapevine, which has become a major threat to European viticulture (Boudon-Padieu, 2002; Chuche and Thiéry, 2014). Symptoms are leaf yellowing or reddening, with downward rolling, incomplete lignification of canes, abortion of flowers, and grape wilting (Caudwell, 1957) It can reduce grape harvests significantly and greatly weaken the vineyards development (Pavan et al, 2012). FDp is transmitted by Scaphoideus titanus Ball (Schvester et al, 1963), a leafhopper living and feeding on Vitis that was accidentally introduced into Europe from North America, one century ago (Papura et al, 2012). With respect to Europe’s situation, this suggests a recent association with Vitis vinifera that occurred when S. titanus invaded South European vineyards, and propagated the phytoplasma on grapevines. Due to its high potential for causing epidemic disease in V. vinifera, FD is listed in Quarantine Pests for Europe, published by the European Union

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Conclusion