Quantitative and qualitative impact of Tomato Black Ring Virus (TBRV) on Merlot and Cabernet franc

Abstract

Aim: Fifteen nepoviruses are able to induce fanleaf degeneration in grapes, which is the viral disease with the highest economic impact. Grapevine FanLeaf Virus (GFLV) is the main causal agent of this disease worldwide and in Europe, followed by Arabis Mosaic Virus (ArMV). A third nepovirus has been described in France: Tomato Black Ring Virus (TBRV), detected in vines for the first time in France on a multi-varietal plot in 2009. The aim of this work is to evaluate the effect of TBRV on grape yield and berry quality potential in two grapevine varieties.Methods and results: Quantitative and qualitative impact of TBRV was investigated in 2010 and 2011 in the vine plot where the virus was first detected in France. Over 200 vines were analyzed by ELISA tests in order to determine their status regarding viral diseases. Vines were distributed in four groups: TBRV positive versus virus free for Merlot and Cabernet franc respectively. For each vine, the presence of eleven other viruses was investigated. In 2010 and 2011 shoot length was measured. Grape composition was also analyzed to determine technological maturity and phenol content in grapes of each vine in relation to its virus status. Total pruning weight was reduced in TBRV infected vines, while lateral shoot number and length were increased. All yield components were affected by the presence of the virus. Vines positive to TBRV produced less bunches and berries and smaller berries compared to healthy vines. Yield loss was greater on Merlot compared to Cabernet franc. Grape quality parameters seemed to be not negatively affected by the presence of TBRV.Conclusions: The major impact of TBRV was a significant yield decrease. The enhanced development of lateral shoots may be considered as a second negative impact that could increase production cost.Significance and impact of the study: These results provide essential information on the impact of TBRV in vineyards. Consequences for management of the viral disease in the vineyard are discussed.