Are Hybrid Winegrapes the Future?

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Most of the wine sold throughout the world is made using Vitis vinifera grapes. Native to the area near the Caspian Sea in southwestern Asia, Vitis vinifera originated in a region and climate that was very different from where it finds itself today—one with fewer temperature swings and weather extremes and one devoid of disease pressures such as powdery mildew.

Other grape species, however, such as the North American V. labrusca and V. riparia, may be better suited to such extreme conditions.

First, some definitions and background.

Vitis (Latin for vine) is the genus name for thousands of different types of grapes, and vinifera (Latin for wine-producing) is the species name that includes such popular winegrape cultivars as Cabernet Sauvignon and Chardonnay.

The words “variety,” “cultivar” and “hybrids” are sometimes used interchangeably, although technically; they refer to very different concepts. A “variety” of grapes (or any other plant) occurs naturally in the wild, while a “cultivar” is a plant with desirable characteristics that has been nurtured and propagated by humans. In contrast, a “hybrid” is something wholly created by humans, either in the field or the lab, and would not exist without human intervention.

Although etymologically distinct, varieties, cultivars and hybrids all originate through a similar genetic process. When genetically distinct organisms reproduce (cross), their genetic material (i.e., DNA) combines to produce something different from either parent. Crosses within species are common (e.g., human babies), whereas crosses between species normally result in non-viable offspring or at least ones that cannot reproduce. A mule—the offspring of a donkey and horse—is sterile, for example.

Natural genetic crosses within the vinifera are common and have naturally resulted in some of today’s most popular wines. For example, Cabernet Sauvignon is the result of a spontaneous cross between Cabernet Franc, Sauvignon Blanc and Chardonnay, sprung into existence from Pinot Noir and Gouais Blanc (Heunisch). Because these originated naturally, Chardonnay and Cabernet Sauvignon started out as varieties, but because they have been propagated by humans for centuries, they are now technically cultivars.

Creating hybrid winegrapes

Normally, species within vinifera self-pollinate, meaning that they are unlike an apple or almond tree and do not require bees or other insects to transfer pollen from one plant to another. Each vinifera grape flower has both male and female parts, and so even a tiny breeze will bring them together to form a viable seed.

The reason that winegrape cultivars are not grown from seed is precisely because this process is so very “easy,” which means that pollen from some other nearby vinifera cultivar might have snuck in. If that’s the case, who knows what new, strange variety each grape-berry seed might contain? Because of this, most vinifera cultivars are propagated by the way of cuttings, which ensures that a perfect parental clone of the original is passed down to the next generation.

But, as we’ve learned, hybrids arise not from naturally occurring crosses but instead when breeders desire particular traits. The mule is an excellent example. Even though not naturally occurring and non-viable from a reproductive standpoint, mules are readily bred for their toughness and tenacity, often used in situations unsuited for either parent.

Are hybrid winegrapes the future?

As our climate changes, many vineyardists are exploring winegrape hybrids as a way to combat the trifecta of extreme temperatures, weather volatility and shifting pest pressures. Hybrids are developed when select cultivars of V. vinifera are systematically crossed with North American species such as V. labrusca or V. riparia.

Because labrusca and riparia evolved in North America, they have built up natural defenses to local conditions. For example, vinifera has no natural resistance to powdery mildew (PM), a fungus prevalent in the Americas but not found in southwestern Asia. If left untreated, PM can spread fast within vinifera, where it can seriously harm both yield and fruit quality. Grape PM, Erysiphe necator, is the most prevalent leaf-infecting disease for California grapes and accounts for nearly 75 percent of grape pesticide use.

The PM example is only one such case. There are other diseases, pests and even the ability to withstand extreme drought conditions that are found in other species of Vitis that might come in handy to future-proof vineyards. So on the one hand, this seems like a pretty straightforward situation: Hybridize all of the good qualities of each species into one plant to get all the benefits of wonderful-tasting wine found in vinifera coupled with the super strong protective power of one of the other species and you are off to the races. Right?

Not so fast. This is going to take some tweaking because as any mule breeder can attest, even when a thoroughbred is crossed with the finest donkey, the resulting mule isn’t likely to win the Kentucky Derby anytime soon.

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