The search is on for disease-resistant grapes
Climate change and recent consumer trends pose a double challenge to vine growers. First, global warming raises the alcohol level in wine when consumers prefer lighter wines, which are viewed as fresher and easier to drink. Second, extreme weather conditions (heatwaves and frost, or droughts followed by heavy rains and hail) are more common than ever before, which multiplies the risk of damages, diseases and pest invasions in the vineyard. Molds, such as mildew and oidium, are a constant threat. The traditional response to such ailments is chemical treatments, but their impact on human health and concerns for the environment are a rising preoccupation. Furthermore, organic, vegan and biodynamic wines, increasingly in demand, simply don’t use these chemicals.
Solutions are not easy to find, but there is hope for certain aspects of the problem, namely when it comes to molds. Some grape varieties have a natural resistance to those diseases but unfortunately they are not members of the Vitis vinifera family. In this age of genomics, research is being done to identify the genetic material that may be responsible for this resistance and to inject it into the Vitis vinifera genome. So far, the results have been rather disappointing: not only was the resistance only partial, but it also diminished with each growing season. Something is missing, so scientists continue to look at interactions among different genes that are not yet fully understood.
Fortunately, another approach has been slowly brewing in the background and is now starting to show very promising results. As a bonus, it can also help with addressing a major problem climate change poses to wine grapes.
Around 40 years ago, a researcher at the Institut National de la Recherche Agronomique’s Pech Rouge lab in France’s Midi region quietly undertook a project to develop naturally resistant vines. His name was Alain Bouquet and he unfortunately died in 2009 before his results received widespread notoriety.
The story begins with a grape variety that has a strong natural resistance to both mildew and oidium, muscadine (of the Vitis rotundifolia family, therefore not vinifera). At the beginning of the last century, curious experimenters were playing around with it, without really understanding where the resistance was coming from. One of the experiments involved crossing it with Malaga seedling, a Vitis vinifera variety from Spain. The resulting new grape was of course only 50 percent vinifera, so it was left aside, but the resistance to both diseases was intact.
Decades later, Bouquet took interest in those experiments and had his first stroke of genius: the resistance being intact in the new grape was a sign that the gene responsible for it was a dominant one, which means it will always express itself when present. He then had a second idea: this unique quality opened the door to a long process of improvement based on something called backcrossing. This technique involves crossing a hybrid variety with one of its parents, or an another genetically similar variety, to produce offspring with more genetic similarity to the parent than the hybrid. The search for a disease-resistant grape was on, and hopes were high. How did he do it?
In his lab, Bouquet fertilized the flowers of the 50 percent vinifera grape with pollen from Cabernet Sauvignon (which is 100 percent vinifera), producing offspring grapes that were 75 percent vinifera. At maturity, the seeds from those berries were removed and planted in soil. Each “child” vine was then left to grow until it produced enough fruit to make wine, which takes a minimum of 4 to 5 years. The grapes of each of those vines were harvested and vinified separately in very small tanks. Why separately, you might ask? In families, most siblings have a unique personality — with different talents, strengths and weaknesses — even if they come from the same parents. The same goes for vines, each child vine was slightly different from the next and the resulting wines were also different. Separate vinification allowed Bouquet to evaluate them individually, and only the most promising ones were retained for the important next step. As the resistance to disease was always present, thanks to its dominant nature, he could concentrate on qualities like lower alcohol potential and better taste. The selected vines were then multiplied through grafting to prepare for the next cycle, which started with a fresh backcrossing.
Over the years, and until his death in 2009, Alain Bouquet went through six more such cycles, each time increasing the vinifera proportion of the new generation. His breedings involved Grenache, Merlot, Sémillon, Riesling and more. Starting with the fourth generation, some of the wines were judged to be of sufficient commercial quality. Thinking that more progress was possible, he continued his work. Today, his followers are still pursuing the project at Pech Rouge. The vinifera content of the latest generation is estimated at 99.2 percent. The time has come to move on to the next phase: out of the laboratory and into the field.
To this end, growers are now invited to lend a portion of their vineyards for planting the new varieties to learn more about how they perform in different soils and microclimates. At present, close to 12 hectares have been planted in the Midi. The objective is to reach 100 hectares in three to four years. These plots are being carefully watched and their wines will be evaluated by experts year after year.
This fascinating story was recounted at a conference held during the latest edition of Terroirs et Millésimes en Languedoc, an annual gathering of wine professionals in Carcassone, France, organized by the Conseil Interprofessionnel des vins du Languedoc.
The conference concluded with a tasting of 16 wines of the last three generations — six whites, three rosés and seven reds. The grapes still have obscure names like 3347 431 and 3176-21-11. However, real names will be given before production starts on a commercial basis. The quality was definitely there. Some of the whites had better acidity and were therefore more fresh; some reds were more tannic than others, but always with good balance and drinkability. The aromas varied from fruity and citrusy to floral and mineral, much like the wines we taste every day. Two of the whites had an alcoholic potential below 11 percent, a sign that the grapes are producing less sugar, a plus as the climate gets warmer. So we may soon have to thank Alain Bouquet for the wine we drink.