From Vines to Wines: A Six-Million Year Journey of Survival
The following text and photos are contributed by Flying Goat Cellars Ambassador Faye Walker:
The Root of It All
When thinking of vineyards, a common scene includes rolling green hills in a sunny swath of countryside. In actuality, the plants themselves are hardy and adaptable and have been known to grow everywhere from urban backyards to high-altitude plateaus. For a sense of how vines have sneaked and snaked across the globe, we need to look back at their biological basis.
Origins and Evolution of Grapevines
Grapevines are classified within the genus Vitis, indigenous only to the temperate Northern hemisphere. The geographic origin of Vitis vinifera dates back over 6 million years. These early progenitors were distant cousins of the vines we see today, being bushy and floral rather than fruity. By 8000 BCE, Vitis had established its stronghold throughout the Americas, Eurasia, and Eastern China. It was only a matter of time before domestication began in 6000 BCE.
Traits of grapevines began to noticeably shift. Fruit and seed size increased, more fruit appeared per cluster, and crop yield was augmented. Sugar levels went up while acid content went down. A major hallmark of domestication, self-fertilization, became possible without the need for cross-fertilization (see image in Figure 1 for morphological differences between wild and cultivated grapevines). And importantly, genetic diversity decreased.
Figure 1. Differences between the leaves, flowers, fruit clusters, and seeds of cultivated (left) and wild (right) grapevines. Adapted from This et al.
As history would have it, glaciation destroyed most of the favorable habitats in the Northern hemisphere (see geographical distribution of cultivars in Figure 2). Only one species survived in Europe during the last ice age: Vitis vinifera. Such was not the case elsewhere. In China, 30 indigenous species made it through. And the Americas? A sizable 34 endemic species persisted.
While the bunch grapes of the Vitus genus can be easily distinguished from other fruits within the Viticeae family, delineating between species is a far more difficult matter. There are confounding factors from species hybridization and environmental influences that make it difficult to tell whether a local population in a vineyard belongs to a certain lineage. It is data derived from molecular DNA markers that offers the clearest interpretation on biological species.
Figure 2. Geographical distribution of genetically differentiated cultivars based on genomic analysis. Clusters C1, C2, and C3 include mainly wine cultivars; clusters C4 and C5 are table cultivars; C6 is Eastern wine cultivars; C7 is Balkan wine cultivars; and C8 is Iberian wine cultivars. Adapted from Laucou et al.
A Family Tree of Today's Rootstalks
Origins of most cultivars are shrouded in mystery across the landmasses from which they arose, with their number seemingly more than the grains of sand on the Pacific shoreline. The existence of multiple and unrelated names for many European cultivars does little to select the common denominators. Not so with genomic analysis, which maps specific genetic markers to build a profile for each clonal mutant within a known varietal.
Amazingly, many classic cultivars have been found to come from a single parent. A cultivar of little modern significance--Gouais Blanc--is the proud parent of Chardonnay, Gamay, Riesling, and Pinot Noir. Other cultivars, although important in terms of progeny, have been kicked to the bottom of the list of viticulture interest. Ever heard of the Benedicto grape? How about Zimmet? Gone by the wayside in the tides of time.
This leads into the fragility of today's most widely-planted grapevines. The number of unique grape cultivars is in the thousands, but only a few of these dominate the commercial viticultural industry. About 75% of these are closely related. The limited genetic diversity is a considerable concern, particularly in the face of ongoing challenges with climate change and disease resistance.
Although standard breeding techniques can successfully select for resistance genes or traits like hardiness, they involve a great deal of time and expense. In addition to the decades-long process, there is an even bigger difficulty: the critics.
Traditional analytical evaluation, targeted marketing, and consumer experience of wines are based around varietals with well-known names from familiar countries. A grape breeding program would require the resulting cultivar to be given a new name, putting it firmly at risk of vinous neophobia.
Overturning Tradition
Is there any future for hybrid grapes selected for genetically desirable features? What about ancient cultivars that no longer fit into today's box of acceptable flavors? While these remnant populations are in risk of extinction, renewed interest in their preservation sheds a glimmer of hope for stabilizing their tenuous existence. The survival of grapes in an ever-changing world may depend on breaking with tradition to embrace a full spectrum of sensory possibilities.
Sources and Further Reading
Jackson, R. S. (2008). Wine science: Principles and applications (3rd ed.). Academic Press.
Laucou V., Launay A., Bacilieri R., Lacombe T., Adam-Blondon A.-F., Bérard A., et al. (2018). Extended diversity analysis of cultivated grapevine Vitis vinifera with 10K genome-wide SNPs. PLoS ONE 13 (2), e0192540.
This P., Lacombe T., Thomas M. (2006). Historical origins and genetic diversity of wine grapes. Trends in Genetics 22, 511-519.