Viticulture is threatened by climate change, but winemakers have several ways to counteract this issue. They can adapt cultivation techniques, for example by modifying plantation density, by setting up irrigation systems, or even by relocating vines to preserve similar climate conditions. However, genetic solutions are also a promising avenue which avoid the need to move vines to new locations; a significant advantage for the wine sector for which the notion of “terroir” [region where the wine is produced] is very important.
Understanding the grapevine
There are specific genetic traits that are sought in vines which are more tolerant to climate change. These include tolerance to hydric stress, resistance to an increase in temperatures or the continued production of tartaric acid (a compound which ensures the grape’s acidity and contributes to the flavour of wine). It must be said that the objective is not to produce a specific molecule or to use a well-characterised gene, for example to increase resistance to a disease. Fitness traits to climate change are often complex, quantitative, coded by several genes which interact together.
Furthermore, vines are to some extent double plants because they are made of both a scion and a rootstock. It is therefore easy to understand the extent of the problem. The scion is the upper part of the plant and its genetic material is expressed through the fruits and leaves. The rootstock, on the other hand, is the underground section and its genes control the root system. Water stress tolerance implicates both roots as well as leaves, and each of which are dependent on a different genome.
To identify a scion/rootstock pair adapted to climate change, one does not just sequence their two genomes and select the pairs carrying the most interesting genes. Our current state of knowledge cannot predict the behaviour of a given pair based only on the sequencing of a few targeted genes. However, it is possible to use genetics to highlight the relationships between the genetic material of a grape variety and its characteristics. To that end, we analyse a large number of grape varieties to identify promising profiles. Our aim is to identify molecular markers on the DNA corresponding to interesting characteristics. We can then use these markers to select varieties without needing to understand the whole complexity of the molecular mechanism. Subsequently, our geneticists ensure that the desirable traits are maintained by studying the descendants of hybridisation.
The creation of a variety by selection of genotypes is a long process. Ten to fifteen years of research are sometimes required, including the legislative timeframes to assess a new grape variety. Most French vineyards are committed to such undertakings. Though they cannot prepare their adaptation in the face of climate change, they can at least cultivate vines that are more resistant to diseases such as mildew or oidium.
Creating new varieties
This approach uses genetics to select the vines most resistant to the effects of climate change. In theory, it is also possible to create these varieties by using genetic engineering techniques. However, in practice, the complexity of the targeted biological systems makes this difficult. We are far from planting genetically modified vines. Other technical impediments also make it difficult to implement this biotechnology. Genetic editing tools, such as CRISPR-Cas9, are harder to use on plant genomes than on animal organisms. Moreover, we still lack the ability to grow vines from just a cluster of cells.
Such practices also seem to raise problems for the consumer acceptability. Indeed, the modification of genomes is not an authorised practice for products sold in Europe and this considerably reduces commercial opportunities. Likewise, wine is a consumer product which is incompatible with potentially controversial debates. Like all luxury products, its production must not raise any questions.