Hybrid vines: adapting winemaking to climate change

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.

Choos­ing characteristics

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.