Influence of environmental factors and cropping practices on grapevine trunk diseases expression and plant-microbiota interaction – GTDfree

The viticulture sector has a significant part in the French agriculture and economy. As regards the cognac, an emblematic sector, it was leader of French exports of wine and spirits industry (sales of € 2.3 billion) in 2014 for the second year in a raw. Hennessy, the world cognac sales leader in the world, exports 97% of its products. This company, present in all continents, is also historically deeply rooted in the Charente vineyards. It now has 75,000 ha of grapevines that have to produce spirits of high quality. It thus requires vigorous plants and a few non-productive grapevines.

The cognac sector and, more generally the wine and spirit sector, seems to be in a favourable position but is nevertheless endangered by many threats that induce profound changes, e.g. climate change and a major plant health crisis, the epidemic of grapevine trunk diseases (GTDs) that endangers the sustainability of the vineyard. Since the ban of the use of sodium arsenite in France in 2001, the only product registered against GTDs, crop losses and uprooting of grapevines increase regularly from year to year, over the last decade. At the present time, it is estimated that around 15% of the cognac vineyard is unproductive. GTDs have a negative impact on the whole French vineyard. For instance, for 2014, losses due to GTDs are huge: 13% of French vineyard is unproductive because of GTDs, it represents a billion euros in losses. This comes quite clearly in contradiction with the viticulture sector development prospects for the next years and those of Hennessy. Driven by its international dimension and fully assuming its leadership role in the viticulture sector, Hennessy has chosen to work on GTDs with UMR SAVE and to grant this research group with an allocation of 600,000 euros. The establishment of an Industrial Chair would enhance this partnership. Research results will benefit to the cognac wine growers partners and more widely to the French and international vineyards.

From a general perspective, this project is designed to limit the development of GTD by using different levers: (i) the cropping practices (e.g. pruning, grafting) that affect the development of necrosis in the wood of the grapevines, a key point to address these diseases. Determining the influence of climate on GTDs will also be investigated, i.e. through irrigation. (ii) Necrosis in grapevine wood tissues are caused by pathogenic fungi, so determining the functions of the wood microbiota will help to get markers linked to the balance break of the microbial communities. This unbalance is linked to the pathogenic process and the subsequent development of wood necrosis. Biocontrol will also be used. Some microorganisms naturally colonizing the vineyards will be used in combination to biologically protect plants against GTDs. (iii) Results from the French GTDs Observatory indicated that grapevines varieties are more or less tolerant to GTDs. So, research on plant molecular polymorphisms associated with plant tolerance or not, seems to be an interesting research topic to determine tolerance markers for breeding.

These complementary points will allow getting a global, systemic view on the development of GTDs at the vineyard. Short-management solutions (e.g. pruning systems, curettage) and medium term (e.g. genetic markers of tolerant plants, healthy cropping practices and "suppressive" microflora) will be proposed at the end of this project.