Cross-protection: mechanisms and applications

Objectives

Cross-protection, a phenomenon discovered almost a century ago, has been used for decades as a biocontrol method to protect plants from damage caused by viral diseases. It consists in inoculating virus variants causing no or little damage to the plant to protect it against subsequent infection by related aggressive variants. In order to develop this biocontrol method effectively and sustainably in the vineyard. Our objectives are to:

• set up greenhouse and vineyard trials to test the efficacy of this method against Grapevine fanleaf virus (GFLV), the main agent responsible for fanleaf disease
• study the diversity and evolution of GFLV
• determine the factors and mechanisms underlying this phenomenon, whose current lack of knowledge hinders the deployment of this method for many pathosystems.

Approaches and resources

GFLV-infected vines showing few or no symptoms were selected from foci heavily affected by the disease in various French wine-growing regions (Alsace, Burgundy, Champagne, Rhône Valley and Bordeaux). Some of these candidate plants - whose variant composition has been determined by high-throughput sequencing (HTS) - have been multiplied and will be replanted by 2027 in their regions of origin in a dozen pilot trials. Phenotypic monitoring (absence of both symptoms and significant yield losses linked to infection by aggressive variants) together with HTS will enable us to determine whether the candidate plants are protected from the serious effects of the disease and from superinfection by other GFLV variants.

In parallel, experiments are being carried out on herbaceous hosts (Nicotiana benthamiana and Arabidopsis thaliana) under controlled conditions to determine the parameters impacting cross-protection (genetic relatedness between protecting and challenging variants, time interval between their inoculations, etc.).

Staff (ViVe team)

• Meryem ALALOUT
• Aleksandar BLAGOJEVIC
• Myriam HAGEGE
• Jean-Michel HILY - IFV
• Olivier LEMAIRE
• Pierre MUSTIN
• Anne SICARD
• Emmanuelle VIGNE

Funding

Vaccivine 2

ProtectMe

Results

In order to select GFLV cross-protection candidates native of Champagne, we studied two Chardonnay plots of this region severely infected by fanleaf disease. The studied vines were classified into three categories: (i) asymptomatic GFLV-free vines (uninfected vines), (ii) virus-infected vines with weak symptoms (cross-protection candidates) and (iii) virus-infected vines with strong symptoms. The four cross-protection candidates selected during this study are being evaluated in trials.

Characterization of grapevine fanleaf virus isolates in ‘Chardonnay’ vines exhibiting severe and mild symptoms in two vineyards. Viruses, 14(10). https://doi.org/10.3390/v14102303