by Nan McCarry
Many of us value landscapes that harbor some wildness. We know that leaving some of the wild and even weedy plants has benefits for wildlife and may provide us with foraged food. We may not realize that some of these also fall into a category called “crop wild relatives,” or wild plants that are closely related to a crop. Breeders often rely on traits found in crop wild relatives to provide the genes for traits that may not be found in the narrower gene pool of a crop. Traits like resistance to pathogens and pests, or the ability to tolerate adverse climatic conditions like drought, heat, or cold are even more important as we face a changing climate. All crops have wild relatives, and it’s one of the most important environmental issues that almost no one has heard of.
Crop wild relatives are often hiding in plain sight. The native grapevines of North America are a good example. Across much of the United States and Canada, you will find native species of grapevine growing along roadsides or property edges. Of the seventy or so members of the grape genus Vitis worldwide, around twenty-five taxa are native to the U. S. and Canada.
Patrice This, Research Director at the French National Institute for Agricultural Research, delighted to find wild Vitis aestivalis growing on a roadside south of Leesburg, Virginia. V. aestivalis is a component of many hybrids and is of great interest to breeders for fungal resistance.
Found among the approximately seventy grape species across the globe is the “domesticated” grape, Vitis vinifera, the source of most of our wine, raisins, and fruit. Domestication is the evolutionary process a plant (or animal) goes through as it comes under human tending and selection and becomes more adapted to an agricultural environment than it is to the wild. According to Dong et al. (2023), the grapevine evolved into its domesticated forms twice around 11,000 years ago in the regions that are currently Western Asia and the South Caucasus. There are, of course, thousands of cultivars or varietals of the domesticated grape—the varietals of V. vinifera which wine drinkers may ask for by name, such as Cabernet Sauvignon or Chardonnay. These are all the same species, and most varietals are genetically quite similar to each other.
Some of the native grapes of North America were the first crop wild relatives to save an industry (Williams & Greene 2018). You may have heard of the phylloxera epidemic that hit European vineyards in the 1860s, devastating the industry. Phylloxera (Daktulosphaira vitifoliae) is an aphid-like insect that evolved in the Americas alongside native grapes (Lund et al. 2017), which can tolerate it feeding on roots and leaves. You can see the nodosities formed when it feeds on leaves of these wild grapes. V. vinifera, however, not having evolved alongside phylloxera, has no natural resistance to it. Phylloxera attacks the roots of V. vinifera and subsequent infections cause the vine to die. Phylloxera had traveled to Europe on grapevines imported from America over much of the nineteenth century, but it is thought that once the steamship was invented, travel was fast enough to allow phylloxera to survive the trip (Gale 2002), prompting the crisis.
After having tried pesticides and many other remedies, the solution to combat phylloxera was found— grafting V. vinifera scions to rootstock from native grapes of North America. Though grafting is a practice thousands of years old, the first use of grafting for winegrape was in response to phylloxera. The native American grape species Vitis riparia and Vitis rupestris were crossed to make rootstock for grafting to V. vinifera. Additionally, because of the need to adapt to the limestone soils of European vineyards, Vitis berlandieri, which grows on the calcareous soils of the Edwards Plateau of Texas, was also incorporated.
Wild Vitis riparia (Grand Rapids, MI). While V. riparia grows across a wide range in the U.S. and Canada, it is still important to conserve the variation in local populations. Photo by Nan McCarry
To this day, a glass of wine that you drink almost anywhere in the world (there are a few regions that remain free of phylloxera) is produced from winegrapes grown on vines grafted to these three and a few other native American species. The value of native grapes for rootstock points to the need to conserve crop wild relatives. One of the native vines that is widely used as rootstock, Vitis rupestris, the rock grape, is ranked as G3 or “Vulnerable” by NatureServe. It used to extend over a much larger range, but is now found mostly in Missouri and Arkansas (Pavek et al. 2003) As an early-successional species adapted to living on sandbars created by periodic flooding and scouring, it is threatened by changes in hydrology due to development (Pavek et al. 2003). In addition, rock grape may be in decline due to hybridization with other species—this is the case with many crop wild relatives, especially grapes, which hybridize readily.
Vitis rupestris, one of the three native grapes that saved the European wine industry, (growing wild in MO). This species grows as a shrub, unlike the vine habit of most grapevines. It is an early-successional species that thrives on gravel bars like this one. Photo by Allison Miller
Another of the three species that saved the European wine industry from phylloxera, Vitis berlandieri, is in decline partly because of expansion of the suburbs of Austin, Texas into the Hill Country. Thousand-acre parcels are being subdivided into lawn-size lots, and homeowners and highway departments are clearing V. berlandieri vines (Walker et al. 2019). What if homeowners had any idea that the vines they are eradicating hold precious germplasm needed for rootstock – that they need them to enjoy a glass of wine?
French ampelographer Pierre Galet collecting Vitis berlandieri in the Davis Mountains in Texas in the 1980s. V. berlandieri is an important component of rootstock and is in decline. Photo by Lucie Morton
A complementary strategy is needed for conservation of crop wild relatives, incorporating both ex situ (off-site) and in situ (in the place the plant naturally occurs) conservation. For ex situ conservation, the USDA maintains a network of stations across the U.S. where crop cultivars and their wild relatives are maintained. The large grapevine collections are in Geneva, New York, and Davis, California. In situ populations continue to evolve alongside biotic and abiotic stressors (pathogens, pests, and weather and climate challenges) and therefore they harbor traits for resistance to or tolerance of these challenges. Because evolution continues on, it’s not enough to keep germplasm frozen in time in a seed bank.
The use of native grapes as rootstock is only part of the story of their importance to the wine industry. Many American grapes have hybridized with Vitis vinifera, both in the wild and via human intervention. Grapes hybridize readily in the wild, and Jun Wen, curator of the grape family Vitaceae at the Smithsonian’s Museum of Natural History, says this is one reason that grape taxonomy is so challenging. Unintentional hybridization between native grapes and domesticated winegrapes first occurred when European colonists brought winegrapes with them to America. Although the European winegrapes usually died, pollen from these domesticated vines occasionally pollinized the native grapes. These chance crossings led to many of our early American cultivars. For example, hybridization with Vitis labrusca, a grape from the eastern United States and Canada, gave rise to many heritage cultivars used for winemaking and table grapes, including Catawba, Delaware, Niagara, Isabella, and of course Concord, which is the grape that gives us grape juice and grape jelly. Read more about the Concord grape’s history here.
Lucie Morton showing the difference in leaf characteristics between the cultivars Norton and Cynthiana in Abilene VA
The Norton is another American heritage grape that readers may know. According to grape breeder and historian Cliff Ambers, “Norton is the most disease-resistant, commonly grown, commercial grape we have.” Ambers’ research shows that Norton is a hybrid bred by Dr. Daniel Norbert Norton in Richmond, Virginia (Ambers 2012), a cross between the European winegrape and the native Vitis aestivalis. Another V. aestivalis cultivar from Virginia is the Cunningham grape. As Lucie Morton, an ampelographer (grapevine botanist) and international vineyard consultant, explains, “Cunningham is now extinct in the United States, and found now clinging to survival only in Brazil, the Azores, Madeira and France.” Morton is working on a documentary on her efforts to repatriate the Cunningham back to the U.S. (https://www.theforbiddenwines.com/en). While Vitis aestivalis is found across much of eastern North America, it still needs documentation and conservation, because there is important genetic diversity across the range of a species and at the population level. This is something that Morton sees while looking at vines in the landscape, and Jun Wen of the Smithsonian is able to detect in genetic studies.
Lucie Morton and Jun Wen examining and marking Norton and Cynthiana grapevines at Casanel Vineyard. These crosses of V. aestivalis are thought to be one and the same but Morton and Wen see a distinction between the two.
As we move towards more sustainable agriculture, it makes sense to support efforts to breed resistance into crops such as the winegrape, which then need fewer chemical sprays and fewer passes through the vineyard with fossil-fueled tractors. Many vineyards and wineries are now offering wines made from hybrid grapes. One that I’m excited about is Dear Native Grapes, located in the Catskills in New York. They are growing a number of hybrid and heritage grapes, including some of the Vitis aestivalis crosses that Cliff Ambers bred in Virginia. Looking towards the future, Vitis aestivalis and other native grapes are being used in new breeding programs, such as a cooperative breeding project with the Virginia Vineyards Association and the USDA Agricultural Research Station in Kearneysville, West Virginia. In this new project, research geneticist Surya Sapkota is breeding grapes resistant to downy mildew and many other diseases prevalent in the mid-Atlantic (Carey 2024).
So what can you do to support one of our most charismatic crop wild relatives, the native grapes? Well, if you’re a wine drinker, exploring what hybrids are available to you locally is one way. Even more important in our work as ecological landscapers is leaving grapevines when possible. It can be a challenge to distinguish wild grapes from other vines, especially invasive porcelain berry (Ampelopsis glandulosa), also in the grape (Vitaceae) family. The leaves of porcelain berry look a lot like grape, but the fruits come in an array of colors. With seedlings, such as those sprouting all over my three acres, it’s hard to tell whether it’s porcelain berry or grape. Jun Wen says that some of the decline of Vitis riparia along the Potomac River has occurred because well-meaning folks are mistaking it for porcelain berry and removing it.
Don’t let this happen to you! A homeowner has mistakenly killed the native grapevine and left the invasive English ivy. Photo by Lucie Morton
Here are two resources that can help you distinguish porcelain berry from grape:
https://www.sleloinvasives.org/invasives/tiered-species-list/porcelain-berry/
The way to tell the difference between grape and invasive vines such as Oriental bittersweet (Celastrus orbiculatas) at any time of year is that mature grapevine (except for the muscadine grape) is distinguished by exfoliating bark. There is also debate about whether grapevines eventually kill the trees they grow on—some say, “no, only invasive vines kill our trees”—but it probably depends on the situation. Of course one may ask why a native tree is more valuable than a native vine, and let nature sort it out.
Resources:
Native Grapes (U.S. National Park Service)
Native-Grapes-NCRN-Resource-Brief.pdf
Follow https://www.organicwinepodcast.com/ to learn more about how hybrids and native grapes are the key to a more sustainable wine industry
References:
Clifford P. Ambers (2013): A historical hypothesis on the origin of the Norton grape. Journal of Wine Research 24:2.
Richard Carey (2024): Searching for cultivars to meet climate change challenges. Wine Business Monthly, (November).
Yang Dong et al., (2023): Dual domestications and origin of traits in grapevine evolution. Science 379.
George Gale (2002): Saving the vine from Phylloxera.
K.T. Lund, S. Riaz, MA Walker M.A. (2017): Population structure, diversity and reproductive mode of the grape phylloxera (Daktulosphaira vitifoliae) across its Native Range. PLOS ONE 12(1).
Diane S. Pavek et al. (2003): Selecting in situ conservation sites for grape genetic resources in the USA. Genetic Resources and Crop Evolution 50.
M.A. Walker et al (2019): Grape taxonomy and germplasm. In D. Cantu and M.A. Walker, eds, The Grape Genome. Springer Nature Switzerland.
Karen A. Williams and Stephanie S. Greene (2018): Conservation of Crop Wild Relatives in the USA. In S. L. Greene et al. (eds.), North American Crop Wild Relatives (Volume 1) Springer Nature Switzerland.
Photo of Nan admiring an old grapevine
Nan McCarry was captivated by the concept of plant domestication in 1981 and has been thinking about it ever since. She received her master’s degree in Geography from the University of Texas at Austin, doing her thesis research in Guatemala on traditional home gardens. For some years she facilitated the sustainable landscaping series “Landscape for Life” in her community, seeking to broaden the discussion beyond native plants to consider our impact on our properties as a whole. She works at Watermark Woods Native Plants in Hamilton, Va. during the season and works on restoration projects on her family’s farms. She is excited to work on this article which brings together two of her favorite topics, crop wild relatives and sustainable landscaping.
Learn more about these topics on her website, ethnobot.org or on her Instagram account @successionalforest
